The correct use of articles in English is complicated by the fact that there are always three possibilities to choose from:
Singular count nouns (nouns that can be counted and have a plural form) REQUIRE an article of some kind. You cannot say: “Cat was sitting on table.” Both “cat” and “table” require an article. The question is which article—definite or indefinite? The answer is: either one. It depends on whether you have in mind a specific cat and a specific table, or whether you mean any cat, sitting on any table. The context provides the answer. Compare:
“A cat was sitting on the table in my kitchen.”
(The cat is of unknown origin; the table is the one in my kitchen.) versus:
“The cat who lives next door was sitting on a table outside.”
(A specific cat, but an unspecified table.)
What makes a noun specific?
“She went to the phone, picked up the receiver, and dialed a number.”
(There was only one phone in the room, and one receiver—but there are many numbers she
might have dialed.)
Plural count nouns (nouns in their plural form), just like singular nouns, may be specified or unspecified. If specified (referring to particular persons or things), they require the definite article “the.” For example:
“The snakes in my garden are not poisonous.” (Which snakes? The ones in my garden.)
If, however, a general remark is being made about ALL snakes, NO article is used:
“Snakes are rarely poisonous.”
“Dogs hate cats.” vs
“The dogs next door hate the cats who live across the street.”
“Winters are severe in Russia.” vs
“The winters I spent in Russia were terrible.”
Noncount nouns (collective nouns) may also be specified or unspecified. Although they look like singular nouns, they are used with zero article whenever they are unspecified:
“Money is easily spent.”
“Time is precious.”
“Jewelry is expensive.”
When specified, they take the definite article:
“The money on the table is mine.”
“Do you remember the time when we first met?”
“The jewelry that was stolen is still missing.”
(For more information on these nouns, see the separate handout Count and Noncount Nouns.)
Proper Nouns are a complex case that must be treated separately. For information on the use of articles with these nouns, see the handout on Proper Nouns.
Singular count nouns must take either “a/an” or “the” (unspecified vs. specified).
Plural count nouns take either zero article or “the” (unspecified vs specified).
Noncount nouns take either zero article or “the” (unspecified vs specified).