Choosing between a/an, the and zero article when speaking generally or specifically.
Articles help distinguish between specific and general meaning.
The choice of article depends largely on whether you are referring to a particular person or thing or to people and things in general.
Use a/an when introducing a singular countable noun for the first time.
The indefinite article presents new information. Once the noun has been introduced, it usually becomes specific.
Use the when referring to something that has already been mentioned or is known to both the speaker and listener.
After a noun has been introduced or identified, it normally takes the definite article.
Use the zero article with plural countable nouns and uncountable nouns when making general statements.
General statements refer to an entire class rather than to specific people or things.
Generic meaning can also be expressed with a singular noun using a/an or the.
Compare: "A tiger is a dangerous animal." and "The tiger is a dangerous animal." Both refer to the species rather than an individual tiger.
Use the when a noun is made specific by a phrase or clause that identifies it.
A following prepositional phrase, infinitive phrase or relative clause often makes a noun definite because it identifies exactly which person or thing is meant.
The same noun may take a/an, the or no article depending on the context.
Article choice depends on meaning rather than on the noun itself. The surrounding context determines whether the reference is specific or general.
Changing the article often changes the meaning of a sentence.
Compare: "I bought a car.", "I washed the car." and "Cars are expensive." Each sentence expresses a different relationship between the speaker and the noun.
Choose articles according to meaning, not according to the noun alone.
Many learner errors occur because articles are chosen by memorizing nouns instead of considering whether the noun is specific, general or identifiable.