Many languages do not use articles (a, an, and the), or if they do exist, they may be used differently than in English. Multilingual writers often find article usage to be one of the most difficult concepts to learn. Although there are some rules about article usage to help, there are also quite a few exceptions. Therefore, learning to use articles accurately takes a long time. To master article usage, it is necessary to do a great deal of reading, notice how articles are used in published texts, and take notes on how to use articles in writing.
Please see this webpage for more about countable and uncountable nouns.
A and an are used with singular countable nouns when the noun is nonspecific or generic.
Sometimes, a or an can be used for first mention (the first time a noun is mentioned). Then, in subsequent sentences, the article the is used instead. when the noun that follows begins with a consonant sound.
A is used when the noun that follows begins with a consonant sound.
An is used when the noun that follows begins with a vowel sound.
The is used with both singular and plural nouns and with both countable and uncountable nouns when the noun is specific. The noun could be specific based on the sentence itself or the context in which the sentence appears.
Here are some more specifics:
The is used in the following categories of proper nouns:
In general, use the with plural proper nouns.
The is often used with proper nouns that include an “of” phrase.
Use the when a noun can be made specific from a previous mention in the text. This is also known as second or subsequent mention.
The is used with superlative adjectives, which are necessarily unique (the first, the second, the biggest, the smallest, the next, the only, etc.).
Biber, Johansson, Leech, Conrad, and Finegan (1999) found that the is about twice as common as a or an in academic writing. This may be because writers at this level often focus on overall ideas and categories (generic reference, usually no article) and on specific references (definite reference, the article the).
Biber, D., Johansson, S., Leech, G., Conrad, S., & Finegan, E. (1999). Longman grammar of written and spoken English. Pearson.
Writers sometimes struggle with the choice to include an article or to leave it out altogether. Keep in mind that if the noun is singular, countable, and nonspecific or generic (e.g., program, researcher), the articles a and an may be used. However, if the noun is countable and plural (e.g., research studies) or uncountable (e.g., information) and it is being used in a nonspecific or generic way, no article is used.
Here are some more specifics:
Sometimes article usage in English does not follow a specific rule. These expressions must be memorized instead.
Here are some examples of phrases where article usage is not predictable:
There are also numerous idiomatic expressions in English that contain nouns. Some of these expressions also contain articles, whereas others do not.
Here are just a few examples: