An and a before a vowel sounding word

Use «a» before words that begin with a consonant sound, and «an» before words that begin with a vowel sound.

Use «a» before words that begin with a consonant sound.

I need to buy a notebook.

I need to buy an notebook.

Use «an» before words that begin with a vowel sound.

There’s an orange on the table.

There’s a orange on the table.

Note that this rule is based on pronunciation, and not spelling. For example, the first letter of the word «European» is a vowel, but it has a consonant sound (a «you» sound). Therefore, it takes the indefinite article «a» (not «an»).

My wife is a European citizen.

Other words, such as «hour» or «honor«, begin with a consonant; however, since the «h» is silent, we use «a» because the initial sound of these nouns is not consonant.

It’s an honor to be your guest.

Follow the same convention to introduce a single letter in a sentence; for example, we say «an F» because the individual letter «F» starts with a vowel sound (similar to «eff«).

Yesterday a bought an expensive necklace with an F on it.

And we say «a U» since this letter is pronounced with a consonant sound («you«).

It’s a U-shaped statistical curve.

A partial list of words and acronyms that begin with a consonant but take the article «an«, and vice versa, can be found below.

Single Letters

As mentioned before, we say «a U» (not «an U»). By contrast, when pronouncing the following consonants as individual letters, we use the indefinite article «an» to say:

• an F
• an H
• an L
• an M
• an N
• an R
• an S
• an X

Words Beginning With EU

Despite beginning with a vowel, the following words start with a consonant sound (a «you» sound), and therefore they take the article «a«:

• a eucalyptus
• a euphemism
• a euphony
• a euphoric
• a euro
• a European

Words Beginning With F

Follow the same strategy with abbreviations that begin with F and are pronounced as individual letters; for example, we say:

• an FBI
• an FDA
• an FYI

Words Beginning With H

These words begin with a vowel sound because the initial letter H is silent. Consequently, they take «an«:

• an heir
• an heiress
• an heirloom
• an herb (American English)
• an herbal (American English)
• an honest
• an honor
• an honorable
• an honorarium
• an honorary
• an hour
• an hourly
• an hourglass

When pronounced as individual letters, these acronyms begin with a vowel sound and are preceded by the article «an» as well:

• an HDL (High-Density Lipoprotein)
• an HDD (Hard Disk Drive)
• an HDMI (High-Definition Multimedia Interface)
• an HIV (Human Immunodeficiency Virus)
• an HPV (Human Papilloma Virus)
• an HTML (HyperText Markup Language)
• an HTTP (HyperText Transfer Protocol)

By contrast, these words begin with a sounded «H» (a consonant sound), so we use the article «a«:

• a habit
• a helicopter
• a hardware
• a historic
• a historical
• a hospital
• a host
• a hostess
• a hotel
• a humble
• a hypothesis

Some English words starting with H, like the ones listed below, can be pronounced in two different ways (either with a silent H or a sounded H). In such a situation, choose the article (a/an) that best suits your own pronunciation:

• a/an herbaceous
• a/an herbicide
• a/an herbivore
• a/an herbivorous

Words Beginning With L

These abbreviations are typically pronounced as individual letters, and therefore take the article «an«.

• an LDL (Low-Density Lipoprotein)
• an LGB (Lesbian, Gay, Bisexual) & LGBT (Lesbian, Gay, Bi, Transgender)

Words Beginning With M

Despite starting with the consonant M, these acronyms are often pronounced as individual letters and take the article «an«:

• an MBA (Master of Business Administration)
• an MD (Doctor of Medicine)
• an MIT (Massachusetts Institute of Technology)
• an MRT (Mass Rapid Transit)

These abbreviations, by contrast, are commonly pronounced as words (milliliter and millimeter) and are usually preceded by a:

• a mL (Milliliter)
• a mm (Millimeter)

Words Beginning With N

Use an before acronyms that begin with N but are pronounced as individual letters; for example, we say:

• an NBA (National Basketball Association)
• an NFL (National Football League)
• an NFT (Non-Fungible Token)
• an NGO (Non-Governmental Organization)
• an NLP (Natural Language Processing)
• an NRA (National Rifle Association)
• an NSA (U.S. National Security Agency)
• an NYSE (New York Stock Exchange)

The Word ‘One’

Note that the word one begins with a “w” sound. Actually, many native speakers pronounce “one” and “won” in the same way. Therefore, we say and write “a one” (not «an one»).

Robert rolled the die and got a one.

Robert rolled the die and got an one.

Words Beginning With R

Use an before acronyms that begin with R and are pronounced as individual letters, so we say:

• an R&D (Research & Development)
• an RGB (Red Green Blue—color model)

But use a if the abbreviation is pronounced as a word and begins with a consonant sound:

• a RAM (Random Access Memory)
• a REM (Rapid Eye Movement—sleep phase)

Words Beginning With S

Because the following acronyms are usually pronounced as individual letters, and the consonant «S» starts with a vowel sound («ess»), we use «an» to say:

• an SEO (Search Engine Optimization)
• an SLA (Service-Level Agreement)
• an SMS (Short Message Service)
• an SMTP (Simple Mail Transfer Protocol)
• an SSD (Solid-State Drive)
• an STD (Sexually Transmitted Disease)
• an SUV (Sport Utility Vehicle)
• an SVG (Scalable Vector Graphics)

Words Beginning With U

The following words begin with a consonant sound («you»), and consequently require the indefinite article «a«

• a unicorn
• a unification
• a unified
• a unifying
• a union
• a unique
• a unit
• a united
• a United Kingdom
• a United Nations
• a United States
• a unity
• a universal
• a university
• a Uruguayan
• a US
• a useful
• a useless
• a user
• a uvula

Follow the same practice with these abbreviations:

• a UFO (Unidentified Flying Object)
• a UID (Unique Identifier)
• a UK (United Kingdom)
• a UN (United Nations)
• a UNESCO (United Nations Educational, Scientific and Cultural Organization)
• a URL (Uniform Resource Locator)
• a US/USA (United States)

Words Beginning With X

Since the pronunciation of the individual letter «X» starts with a vowel sound, use the indefinite article «an» before these abbreviations:

• an X-ray
• an XL (eXtra Large)
• an XML (eXtensible Markup Language)

When is the correct time to use a vs. an?

• A bike.
• An icicle.
• A URL or an URL?

What exactly is the rule? Despite the confusion on when to use these two words, the rule regarding their use is actually quite simple.

What is the Difference Between A and An?

In this post, I will compare a vs. an. Both words are articles and are extremely common in the English sentence. As such, I will go over the general rule for a and an and use each in multiple example sentences.

The basic rule for using a in a sentence is

• Use a before words, abbreviations, acronyms, or letters that begin with a consonant sound, regardless of their spelling.

For example,

• A dog.
• A fish.
• A university.
• A utopia.

The important part is the sound of the word that follows, not necessarily the letter with which it starts. The above examples have words that begin with vowels and consonants, but we use a for all of them because they begin with the sound of a consonant. More on this below.

When to Use An

An is used before words, abbreviations, acronyms, or letters that begin with a vowel sound, regardless of their spelling.

• An idiot.
• An element.
• An honor.
• An heirloom.

The rule only becomes tricky when you have a vowel with a consonant sound or a consonant with a vowel sound like in our above examples,

• A university (yoo-ne-ver-se-tee).
• A utopia (yoo-toe-pe-a).
• An honor (ah-ner).

When you come across these, ignore what the first letter is and just listen to the sound that it makes. Say the word out loud. If it sounds as if it is beginning with a consonant sound, use a. If it sounds as if it is beginning with a vowel sound, use an.

What if an Adjective is Added in Front of a Noun?

Some people aren’t sure how to apply this rule when an adjective appears before the noun being referred to.

For example, which of these are correct?

• I went to an exciting concert last night. (CORRECT)
• I went to a exciting concert last night. (WRONG)

The same rule still applies. “A” is used before words starting in consonant sounds and “an” is used before words starting with vowel sounds. It doesn’t matter if the word is an adjective, a noun, an adverb, or anything else; the rule is exactly the same.

Problem Words with An vs. A

There is, however, some disagreement (although it is decreasing year by year) on how to treat certain words that begin with “h,” specifically historic and historical.

But how can that be? Ask any English speaker today to say “historic” and you will almost invariably hear a distinct “h” sound at the beginning of the word.

English speakers of today might pronounce “historic” with an “h” sound, but The American Heritage Dictionary has a wonderful usage note explaining how that was not always the case.

In the usage note, American Heritage states that “an” was at one time a more common variant before words beginning with “h,” words where the first syllable is now unstressed. This is why you will quite routinely see in 18th-century literature both “a historical” and “an historical.” Back then, this usage made logical sense because many people did not pronounce the “h” at the beginning of the word. The usage note goes on to say that “by the late 19th century educated speakers usually gave their initial h’s a huff, and the practice of writing an before such words began to die out.”

You will still see “an historical” in writing every now and then and, although The American Heritage Dictionary says that both forms acceptable in formal writing, “an historical” should be avoided. Both The Chicago Manual of Style and The AP Stylebook hold that “a historic” is the proper form.

There are a few other problem “h” words out there. Here is a list of most of them and their proper forms.

• An hour.
• An honor.
• An honorary degree.
• A hysterectomy.
• A heredity trait.
• An heir.
• An heirloom.
• An herb.
• A humble man.
• An homage to the fallen.

As we said above, this rule also applies to acronyms and initialisms. Whether or not to use an or a depends on the pronunciation.

• An NBC television show.
• An HTML document.
• A CBS news outlet.
• A Microsoft program.

-but-

• An MS-DOS program.

So, to answer our opening question about URLs, it should be a URL since URL is normally pronounced U-R-L.

Summary

Is it a or an? Both a and an are used as articles in the English sentences, but their use use differs based on what words follow.

How to Use A and An:

• A is used with consonant sounds.
• An is used with vowel sounds.

The indefinite articles a and an pop up all over the place, introducing nouns that refer to people, creatures, or things not identified or specified. We see and hear them in phrases like «a dessert» and «an essential.» Native speakers of English often give them no thought at all: the little words just slip off the tongue like nearly invisible thread linking more important lexical elements.

In a way, a and an are the same word. They both trace back to the Old English word ān, meaning «one,» and they both have had the same indefinite article function since the days of Middle English.

And yet, they appear in slightly different contexts.

The patterns that determine which article, a or an, is conventionally used before a given word are based on phonetics, but the patterns exist in writing as well as speech. When preceding a consonant sound, a is used: «a cake,» «a slice of cake.» Before a vowel sound, an is usual: «an enormous slice of cake,» «an appropriately enormous slice of cake.» But sometimes, typically in speech and more frequently in some dialects than others, a is found before a vowel sound: «a ambrosial cake.»

The pattern exists for consonant sounds represented by a vowel letter as well: «a one-handed attempt at cake serving,» «a united effort to distribute cake equitably.» An is sometimes used in such contexts, but less now than it was in the past: «an unique opportunity for equitable ambrosial cake serving.»

The letter H has historically inspired its own set of rules. When the word beginning with H has a first syllable that is unstressed or only weakly stressed, both a and an are used: «a hilarious joke used to distract us during an horrific cake theft.» This is, however, less true than it used to be; a is now the typical choice before words beginning with H no matter their stress patterns. This is even true for the most famous examples: the word historic and its relations. While «an historic cake theft» and «an historical perspective on the theft of cake» will likely not earn you the opprobrium of your readers/listeners, «a historic» and «a historical» are by significant margins more popular. Do with that what you will.

Also H-related: in the King James Version of the Old Testament, you will find an used before H in a stressed syllable as well: «an huntress,» «an hundred.» In modern speech and writing this is rarer than even the most ambrosial cake.