The word change is a verb

Your two examples each illustrate one of two types of English verbs forms — finite and non-finite. The former (in your second sentence) is the verb in the predicate of the clause

[1a] how people change throughout their lives

Finite verbs carry the sense of a verb — conveying actions, the states of things, feelings, or equivalences. Finite verbs may be inflected for tense and number. Here change is in the present tense, but it is possible to transpose your sentence to the past tense with

[1b] how people changed throughout their lives

Your first sentence has a non-finite form of the verb, namely the infinitive, which is formed by the word to plus the plain form of the verb. (The to is elided in certain cases, as in

[2] We must [to] change our lives immediately.

This is called the bare infinitive.)

Non-finite verbs are not inflected for tense. It is not grammatical to say to changed. Infinitives find usages in sentences other than as verbs in predicates. In your first sentence, the infinitive takes the place of a noun phrase as the object of the verb began. But it could act as an adverb of purpose:

[3] I came to change the furnace filter.

No matter its usage in a sentence, we still call the infinitive a verb because it acts syntactically in many ways like a verb, e.g, it can take a direct object (that would be furnace filter in [3]).

From Longman Dictionary of Contemporary EnglishSport, Babies, Currencies, Transport, Motor vehicles, Naturechangechange1 /tʃeɪndʒ/ ●●● S1 W1 verb
 
 1 become different/make something different [intransitive, transitive]CHANGE/BECOME DIFFERENT to become different, or to make something become different
 Susan has changed a lot since I last saw her.
 Changing your eating habits is the best way to lose weight.
 The leaves on trees change colour in the autumn.change (from something) to something
 He changed from being a nice lad to being rude and unhelpful.change into
 The hissing sound gradually changed into a low hum.change somebody/something into something
 A witch had changed him into a mouse.change something to something
 Mueller changed his name to Miller when he became a U.S. citizen. 2 start doing/using something different [intransitive, transitive]DS to stop doing or using one thing, and start doing or using something else instead SYN switch
 She changed jobs in May.change (from something) to something
 The company has recently changed to a more powerful computer system.
 The ship changed course and headed south.
 The company has had to change direction because of developments in technology.
 Piper awkwardly tried to change the subject (=talk about something else).

3 replace something [transitive]REPLACE to put or use something new or different in place of something else, especially because it is old, damaged, or broken
 Three boys were changing a tyre by the side of the road.
 When I lost my keys, we had to change all the locks.change something (from something) to something
 The time of the meeting has been changed from 11:00 to 10:30.
 How often do you change cars (=buy a new car and sell the old one)? 4 → change your mind5 → change sides6 clothes a) [intransitive, transitive]TAKE OFF CLOTHES to take off your clothes and put on different ones
 Francis came in while Jay was changing.
 Change your dress – that one looks dirty.change into/out of
 Sara changed into her swimsuit and ran out for a quick swim.
 You’d better go and get changed. b) [transitive]DHB to put a clean nappy on a baby, or to put clean clothes on a baby or small child
 I bathed him and changed his diaper.
 Can you change the baby?

7 bed [transitive] to take the dirty sheets off a bed and put on clean ones8 exchange goods [transitive] British EnglishEXCHANGE a) to take back to a shop something that you have bought and get something different instead, especially because there is something wrong with it SYN exchange American Englishchange something for something
 I bought these gloves for my daughter, but they’re too large. Can I change them for a smaller size? b) to give a customer something different instead of what they have bought, especially because there is something wrong with it SYN exchange American English
 I’m sure the shop will change them for you.9 exchange money [transitive] a) EXCHANGEto get smaller units of money that add up to the same value as a larger unit
 Can you change a £20 note? b) PECto get money from one country for the same value of money from another countrychange something into/for something
 I want to change my dollars into pesos, please. 10 trains/buses/aircraft [intransitive, transitive]TT to get off one train, bus, or aircraft and onto another in order to continue your journeychange at
 Passengers for Liverpool should change at Crewe.change trains/buses/planes etc
 I had to change planes in Denver.all change! (=used to tell passengers to get off a train because it does not go any further)

11 → change hands12 → change places (with somebody)13 gearTTC [intransitive, transitive] to put the engine of a vehicle into a higher or lower gear in order to go faster or slowerchange (into/out of) gear
 Change into second gear as you approach the corner.change up/down British English
 Change down before you get to the hill. 14 → change your tune15 wind [intransitive]DN if the wind changes, it starts to blow in a different direction16 → change your spots → chop and changeGrammarChange belongs to a group of verbs where the same noun can be the subject of the verb or its object. • You can say: They’ve changed the password. In this sentence, ‘the password’ is the object of change.• You can say: The password has changed. In this sentence, ‘the password’ is the subject of change.COLLOCATIONSadverbsdramatically/drastically/radically (=a lot)People’s work environment has changed dramatically in the past twenty years.completelyHis life had completely changed since he met Anya.considerablyHe has changed considerably in four years.significantlyThe legal system has changed significantly since the rule was established.fundamentallyThe political situation has fundamentally changed.rapidly/quicklyThe market for phones is changing rapidly.slowly/graduallyThings are gradually changing.change overnight (=very quickly)Old habits cannot be changed overnight.nounschanging circumstances/conditionsThe human brain adapts quickly to changing conditions.changing attitudesChanging attitudes cause traditional ways of life to disappear.the changing role of somebodythe changing role of women in societychanging patterns of work/behaviour etcChanging patterns of work mean that more people are able to work from home.a changing environmentIn order to survive, you must adapt to a changing environment.a changing worldChildren are growing up in a changing world.changing times (=a period of time when a lot is changing)We live in changing times.

THESAURUSto change somethingchange to make someone or something differentUnfortunately, there’s nothing we can do to change the situation.Being at college has changed her – she’s much more confident now.alter especially written to change something so that it is better or more suitableYou can alter the colour and size of the image using a remote control. Can we alter the date of the meeting?adapt to change something slightly in order to improve it or make it more suitableHow much would it cost to adapt the existing equipment?You can adapt the recipe to suit your own requirements.adjust to make small changes in the position or level of something in order to improve it or make it more suitableHow do you adjust the volume on the television?He adjusted his tie in the mirror.modify especially written to make small changes to something such as a piece of equipment, a set of ideas, or a way of behaving in order to improve it or use it in a different wayHe’s modified his opinions since then.a modified version of the original programreform to change a law, system, organization etc so that it is fairer or more effectiveplans to reform the tax systemHealth care needs to be completely reformed.revise to change a plan, idea, law etc because of new information and ideasIn July, China revised the rules for foreign investment.The findings could force the scientists to revise their ideas about climate change. reorganize to change the way that a system or organization worksWe’ve had to reorganize our database.During the 1980s, the government reorganized the civil service. restructure to make big changes to the way something is organized, especially a large political or economic system or a big company, in order to make it more effectiveThe company has been restructured from top to bottom.to change something completelytransform to change something completely, especially so that it is much betterWell, you’ve certainly transformed this place – it looks great!Putin transformed the Russian economy.revolutionize to completely and permanently change the way people do something or think about something, especially because of a new idea or inventionComputers have revolutionized the way we work.This important discovery revolutionized our understanding of the universe.to change something in order to deceive peopledistort to explain facts, statements etc in a way that makes them seem different from what they really areThe judge said that she had deliberately tried to distort the facts.Don’t try to distort the truth.twist to dishonestly change the meaning of a piece of information or of something that someone has said, in order to get an advantage for yourself or to support your own opinionHe accused reporters of twisting his words.In her article she twisted the meaning of what I said.misrepresent to give people a wrong idea about someone or their opinions, by what you write or sayI hope I have not misrepresented her opinion.He’s taking legal action to stop the film, claiming it grossly misrepresents him.

→ change something ↔ around → change over→ See Verb tableExamples from the Corpuschange• I’m just going upstairs to change.• I think the batteries need changing.• As people in other staff agencies sought to perform differently and better they also improvised, learned, and changed.• Can you change a $10 bill?• All drivers should really know how to change a flat tire.• Her expression did not change, and she answered me calmly.• I can’t believe it’s been ten years — you haven’t changed at all.• «The telecommunications industry is changing at lightning speed, » said Richard Miller, the company’s chief financial officer.• But he will change course if the market demands it.• I tried to follow him but he kept changing direction.• It is rugged country whose landscape changes every few kilometers.• Going to college changed him a lot. It made him much more mature.• Each has the right to change its status in this respect, subject to relevant agreements and procedures.• You have changed, Joan de Warenne, she thought.• Do you mind waiting while I change my clothes?• Going to college really changed my life.• I’ll just change my shirt and I’ll be with you in a minute.• The bill requires health insurers to maintain coverage for anybody who changes or loses his job.• This is another area which is changing out of all recognition since closure of the colliery and removal of sidings etc.• Ed went into the bedroom to change out of his work clothes.• How does the President plan to change the tax system?• What tragedies must occur before he and the Minister of State will change their minds?• If the trousers are the wrong size you can always change them.• Can you change this light bulb for me? I can’t reach.• Agriculture must be changed to reduce damage to the environment.• «Have you got your bathing suit on?» «No, I’ll change when we get there.»• Having a baby changes your life completely, whatever your age.

change (from something) to something• In contrast, pragmatic parties hold more flexible goals and are oriented to moderate or incremental policy change.• The company realized they could actually save money if we changed to a modern computerized system.• They sometimes contain concrete examples of changes which need to be made.• The change from communism to democracy has been very difficult.• As a result, tracing changes directly to human actions has proved difficult.• The water on the bridge had changed to ice during the night.• To make those changes but to maintain the essential spirit of cricket is the continuing challenge.• A few changes seem likely to produce noticeable ripples in 1997.• Be prepared to change the conversation to something more personal.• An organism adapts to another when it changes itself to suit the latter.• Concern over the changes in lifestyle to undertake the job.change (from something) to something• In contrast, pragmatic parties hold more flexible goals and are oriented to moderate or incremental policy change.• They sometimes contain concrete examples of changes which need to be made.• As a result, tracing changes directly to human actions has proved difficult.• To make those changes but to maintain the essential spirit of cricket is the continuing challenge.• A few changes seem likely to produce noticeable ripples in 1997.• Be prepared to change the conversation to something more personal.• An organism adapts to another when it changes itself to suit the latter.• Concern over the changes in lifestyle to undertake the job.

change something (from something) to something• The budget line changes from 12 to 13.• Be aware that fraudulent businesses often change their names to avoid detection.• Humanist psychology’s caution about change can add to egalitarian feminist psychology’s existing theoretical timidity.• At a local level, Gloucester’s changes were largely confined to filling gaps left by the removal of the Woodvilles.• It may not be happening fast enough, but the winds of societal change take a while to get up to speed.• The change from adversity to prosperity, according to Aristotle, fails to produce the proper tragic effect.• Hasn’t it been changed over the years to say different things from what the original writers intended?• All psychiatric problems are brain problems, and the psychiatrists are changing their classification scheme to try and avoid that cartesian dichotomy.change into/out of• He had actually changed out of his cricket gear, showered and packed up his kit.• It was a shame he didn’t have time to change out of his gardening clothes before he appeared on the show.• Alistair was just getting off the phone when I came in to change out of my good clothes.• The other day I was in a hurry and struggling to get the right change out of my pocket for the newsagent.• I changed out of my work clothes and into my denims and shirt to get into the mood.• School meals have changed out of recognition within a generation.change something into/for something• I want to change my dollars into pesos, please.change trains/buses/planes etc• I stopped there only to change trains.• It shows passengers where they need to change trains.• We parted at Paddington, and assured them that they would have to change trains at Oxford.• Although the line will remain open, people will have to change trains at Thornaby.• There is an unutterable sadness around Medina del Campo, where I had to change trains for Salamanca.• They might not even tell you that changing planes in Dallas or leaving Thursday instead of Friday will save you a bundle.change (into/out of) gear• Any cyclist can climb a difficult hill: you just change gear.• With him came a difference in style, a change of gear, a time for reflection and taking stock.• Russ Armstrong, a Middlesbrough motorcycle dealer, has also changed gear after 18 years of the road racing power game.• Volkov changed gear and increased his speed.• You need to be able to move swiftly, changing gears and learning new skills without complaining.• In effect I reckon it will only take a slight upward change of gear and performances to become something special.• Mark’s idea of getting her to change gear was to slip on a nurse’s uniform.Transportchangechange2 ●●● S1 W1 noun
 
 1 things becoming different [countable, uncountable]CHANGE/BECOME DIFFERENT the process or result of something or someone becoming different
 I find it hard to cope with change.
 scientists worried about climatic changechange in
 changes in the immigration laws
 A change in personality may mean your teenager has a drug problem.change of
 a change of temperature
 No major changes were made to the book.change for the better/worse (=a change that makes a situation better or worse)
 There was a change for the better in the patient’s condition.social/political/economic etc change
 the sweeping political changes after the fall of communism
 She had a change of heart (=change in attitude) and decided to stay.
 Family life has undergone dramatic change in recent years.2 from one thing to another [countable]CHANGE FROM ONE THING TO ANOTHER the fact of one thing or person being replaced by another
 The car needs an oil change.change of
 a change of government
 a change of addresschange from something to something
 the gradual change from grasslands to true desert
 The government has made some major policy changes.3 pleasant new situation [singular]DIFFERENT a situation or experience that is different from what happened before, and is usually interesting or enjoyablechange from
 The morning was cool; a welcome change from the heat of the day before.for a change
 How about dinner out for a change?it/that makes a change (=used to say that something is better than and different from usual)
 ‘Ron’s buying the drinks.’ ‘That makes a change.’change of scene/air/pace etc (=when you go to a different place or do something different)
 The patients benefit greatly from a change of scenery.a change is as good as a rest (=used to say that starting to do something different is as good as having a rest)4 money [uncountable] a) MONEYthe money that you get back when you have paid for something with more money than it costs
 Here’s your change, sir. b) money in the form of coins, not paper moneyin change
 I have about a dollar in change.
 Matt emptied the loose change from his pockets.
 A beggar asked for some spare change (=coins that you do not need). c) coins or paper money that you give in exchange for the same amount of money in a larger unitchange for £1/$10
 Excuse me, have you got change for a pound?make change American English (=give someone change)
 Can you make change for $20?► see thesaurus at money5 → small change6 → change of clothes/underwear etc7 train/bus/aircraft [countable]TT a situation in which you get off one train, bus, or aircraft and get on another in order to continue your journey
 Even with a change of trains, the subway is quicker than a cab at rush hour.8 → get no change out of somebody → ring the changesCOLLOCATIONSadjectivesbig/majorGoing to a new school is a big change for children.slight/small/minorThe proposed changes were relatively minor.gradualThere has been a gradual change in the weather.dramatic/drastic/radical (=very big, especially in way that is surprising)The Industrial Revolution was a period of dramatic change.significantThe change in blood pressure was not significant.marked (=very noticeable)There was a marked change in his behaviour.fundamentalReducing waste requires a fundamental change in attitude.social/political/economic etc changeDemands for political and social change are growing.sweeping changes (=affecting many things or people, especially because of an official decision)There are likely to be sweeping changes in the company.far-reaching changes (=important and having a great effect that will last a long time)The Internet has brought about far-reaching changes in the way we work.verbsmake a changeWe’ve had to make some changes to the design. introduce a changeA number of changes were introduced to the curriculum.bring (about) change (also effect a change formal) (=cause change)The war brought about radical social change.Treatment is aimed at effecting a change in the child’s negative behaviour.see/notice/observe a change I saw a big change in her when I met her again.undergo a change (=be affected by a change)The body undergoes a number of changes during this time.signal a change (=be a sign of a change)Does this move signal a change in US foreign policy?phrasesthe pace/rate of changePeople sometimes feel alarmed by the pace of technological change.THESAURUSchange noun [countable, uncountable] a situation in which someone or something becomes different, or the act of making something differentThere was a sudden change in the weather.We are living in a period of great change.He was told to make some slight changes to his essay.alteration noun [countable, uncountable] a change, especially a small one that happens naturally or gradually, or one that is made in order to improve somethingI noticed a slight alteration in her behaviour.They had to make some alterations to their original theory. reform noun [countable, uncountable] a change made to a system or law in order to improve itHe called for a reform of our outdated voting system.Many people opposed the economic reforms.shift noun [countable] a change, especially in people’s attitudes or in the way they do things, or in the position of someone or somethinga shift in public opinion about the warThere has been a noticeable shift in government policy on education. There needs to be a major shift away from road transport to rail transport.After he died, there was a dramatic shift in the balance of power.swing a big change, especially in someone’s opinions or moodsThere has been a big swing toward the Democrats (=many more people are supporting them).The drug can cause mood swings.fluctuation noun [countable, uncountable] a change in something – used when something changes oftenfluctuations in the value of the dollartemperature fluctuationsfluctuations in his moodThere has been some fluctuation in productivity levels.a great changetransformation noun [countable, uncountable] a change in which something or someone becomes completely differentThere has been a complete transformation in his attitude since he became a father.her transformation from shy local girl to famous movie actressrevolution noun [countable] a complete change in ways of thinking or workingThe 1970s saw the beginnings of a new technological revolution.Einstein’s General Theory of Relativity started a revolution in scientific thinking.shake-up noun [countable] a situation in which a lot of changes are very quickly made in a system or organization in order to make it more effectiveThe department has not performed well and is badly in need of a shake-up.The Administration is planning a thorough shake-up of the welfare system.U-turn noun [countable] a complete change in the plans of a government or political party so that it decides to do the opposite of what it originally said it would doThe government was forced to do a U-turn after angry protests about their taxation policy.Examples from the Corpuschange• If you are thinking about a change to a different part of the country you will need to use your vacation to look for accommodation.• The delay was the result of a change in the way that we administer the grants.• For most ordinary workers, the new tax laws represent a change for the worse.• Two events occurred that ensured, for the time being at least, no such a change in Congressional attitudes would occur.• Many people find it hard to accept change.• He hates all changes to his routine.• The police must be notified of any change of address.• The computers will record any changes to the system.• After a number of career changes, she settled into a job with a major bank.• Does anyone have change for a five dollar bill?• I’ve got a £10 note and about £5 in change.• I’ve got £20 and a bit of loose change as well.• Labor Secretary Lynn Martin recommended major changes in the management operations of the company.• I expect to see major changes until it is ten years old.• Volatility increased, and the extent as well as the direction of change became less predictable.• A lot of people are frightened of change.• 1989 was a year of great political change in eastern Europe.• These spectacles are in fact subject to relentless change.• I hope you’ve got some change for the bus, because I haven’t.• Some changes have already been introduced into schools.• The movie pivots on not one but two such changes, and the result is exhaustingly cathartic, ultimately uplifting.• French people were asked how they felt about the change from the franc to the Euro.• I can’t get used to all these changes.• House plants are often sensitive to changes in temperature.• Excuse me, I think you’ve given me the wrong change.• Here is your change, sir.change in• Changes in diet can reduce the occurrence of some cancers.• A change in personality can mean your teenager has a drug problem.change from something to something• The abrupt change from legacy to trust is very striking.• The mean period is 331 days, but both the period and the amplitude change from one cycle to another.• The curriculum, which at one time had seemed novel, barely changed from decade to decade.• It is a time-phase between childhood and adulthood and a process of changing from a pupil to an independent working adult.• Nevada City is in process of changing from old to new.• The performers changed from summer to summer, but the scene remained the same over many decades.• She felt light-headed and it was not just the swift change from lying down to standing.• Why that change from symmetrical expansion to uneven ejection took place is a mystery, Bond said.change from• Living in Iowa is certainly a big change from Florida.in change• The clerk handed him $3 in change.From Longman Business Dictionarychangechange1 /tʃeɪndʒ/ verb [transitive]1to exchange a unit of money for smaller units that add up to the same valueCan you change a £20 note?2to exchange money in one currency into money of another currencyI want to change these dollars into Euros.3to exchange something that you have bought, especially because there is something wrong with itWe will only change goods accompanied by a receipt.4change hands if property changes hands, it passes from one owner to anotherVolume was heavy on the NYSE, where about 2.19 billion shares changed hands.→ See Verb tablechangechange2 noun [uncountable]1the money you get back when you have paid for something with more money than it costsShe received a forged banknote in her change.You won’t get much change from a ten pound note here.2money in the form of coins and notes of low valueI have about a dollar in change.I didn’t have any small change for the telephone.Origin change1 (1100-1200) Old French changier, from Latin cambiare “to exchange”