Definite and Indefinite Articles (a/an/the)

An article is an adjective (a determiner) that comes before and modifies a noun or noun equivalent.

Articles indicate whether a noun is specific or unspecific. The definite article (“the”) defines a noun as specific, which means that the identity of the noun is known. An indefinite article (“a” or “an”) defines a word as unspecified, which means that the identity of the noun is unknown.

Example
The flower smells nice.
Example
A flower smells nice.

The first example states that there is one specific flower that smells nice. The second is a general statement: “any flower smells nice” or “all flowers smell nice.”

What are Definite Articles?

The definite article “the” indicates that a noun has a specific identity and/or that it has already been referred to once before in the context of a given piece of writing.

Example
The gallery teaching program was designed for the Whitney Museum of American Art.

Here, the “gallery teaching program” is a specific program that was designed for a specific museum (i.e., the Whitney Museum of American Art).

Example
These three methods of fabricating the composite were demonstrated to be the most efficient.

The “composite” is one specific composite. It can be presumed from this sentence that this composite was previously identified.

Example
Chronic anxiety was found to significantly increase the likelihood of Alzheimer’s in later life.

“Likelihood of Alzheimer’s” is an uncountable noun. However, here it is a specific uncountable noun.

When to use definite articles

Noun Type Usage Example
Countable noun

An entire, specific group

One specific, countable thing

The refrigerator was invented in 1834.

The earth is not perfectly round.

Uncountable noun

One specific, uncountable thing

Noun 1 + of + Noun 2

The evidence is indisputable.

Sally is the mother of the child.

What are Indefinite Articles?

Indefinite articles “a” and “an” are used to indicate that a noun has an unspecified identity.

Example
The addition of an external heating system, while useful, continuously consumes power and weighs down the vehicle.

Here, “external heating system” is not a specific heating system; any heating system would be useful but would also continuously consume power and weigh down the vehicle.

Example
“Fragmentary Blue” is a poem by Robert Frost.

Robert Frost wrote many poems and “Fragmentary Blue” is one of them.

Example
An irregularity was identified in the composite.

It can be presumed from the indefinite article “an” that this “irregularity” was not previously established. Any future reference to this particular irregularity should use the definite article “the.”

Example
An irregularity was identified in the composite. The irregularity was caused by a leak in the vacuum chamber.
Noun Type Usage Example
Countable noun

One member of a countable noun

First mention of a countable noun

I would like a book on scorpions.

We found an anomaly.
The anomaly was unexpected.

Uncountable noun

Never used with indefinite article

N/A

Choosing “a” or “an”

The choice between “a” and “an” depends on the sound the following word begins with. The article “a” precedes words that begin with a consonant sound; the article “an” precedes words that begin with a vowel sound. For example, the word “apple” should be preceded by “an.” This is because the word “apple” begins with a vowel and a vowel sound.

Example
A good notebook should have a sturdy cover and tear-resistant paper.
Example
I peeled an orange for my sister.
Example
An SSD contains nonvolatile flash memory.

Using indefinite articles with uncountable nouns

Indefinite articles typically cannot be used with uncountable nouns.

Incorrect
There is a snow outside.
Correct
There is some snow outside.

This is incorrect because “snow” is an uncountable noun. There are, however, certain uncountable nouns that are sometimes treated as countable. This is generally only applicable to casual, non-academic contexts.

Example
I will have a coffee.
Example
Can you pass me a sugar?

It can be assumed here that “a coffee” is being used to mean “a cup of coffee.” The same applies to “a sugar”; “a sugar” can be assumed to mean “a cube of sugar.”

Applying an Article Before an Adjective

A noun that is modified by an article is often also modified by another adjective. In such cases, the article typically comes from and then is followed by the adjective and noun.

Example
An unusual dent was identified in the composite.
Example
We propose an effective method of regulation.
Example
The first basic method of modeling was based on a differential equation model.

Articles with Pronouns

Articles cannot be used with pronouns. This is because both articles and pronouns indicate specificity and using both would only cause confusion.

Incorrect
Here is the your computer.
Incorrect
Can you help me find a my notebook?

However, depending on the context, a definite article and a pronoun may be used interchangeably.

Example
Here is the computer.
Here is your computer.

When to Omit an Article

In some cases, an article can be omitted before a noun because the article is implied and does not need to be explicitly written. Articles are usually omitted before (1) languages / nationalities, (2) academic subjects / fields of expertise, and (3) certain abstract ideas.

Referring to languages and nationalities

Articles are always omitted before languages.

Incorrect
Phil is learning the Japanese.
Correct
Phil is learning Japanese.

Depending on the context, articles are also omitted before nationalities.

Example
Lana is the American.

The above sentence implies that there are multiple people but only one American (and her name is Lana).

Example
Lana is American.
Lana is an American.

These sentences, on the other hand, simply mean that Lana’s nationality is American.

Referring to academic subjects and other fields of expertise

Academic subjects and other fields of expertise, such as sports, are also not preceded by articles.

Incorrect
He studies the physics at university.
Correct
He studies physics at university.
Incorrect
The gymnastics is a highly demanding sport.
Correct
Gymnastics is a highly demanding sport.

Referring to some abstract ideas

Articles are generally unnecessary when writing about abstract ideas because an abstract idea is not a specific thing, and articles are used to indicate specificity.

Incorrect
The beauty is in the eye of the beholder.
Correct
Beauty is in the eye of the beholder.
Incorrect
The love is blind.
Correct
Love is blind.