Only countable nouns require articles.
Countable nouns are people, places, or things that can be counted (i.e. one bottle, two bottles...). Non countable nouns cannot be made plural (i.e. milk, life, water, love).
Articles are indefinite or definite.
An indefinite article is "a" or "an." Each means "one" (i.e. a pony). Indefinite articles are general.
A definite article is "the." It is specific, the only one (i.e. the pony).
To determine whether to use an article and, if so, which one to use, follow these steps:
- Is the noun countable? If no, stop because no article is needed. If yes, proceed.
- Is the noun a specif one or one of many? If specific, use "the." If general, proceed.
- Is the noun plural or singular? If plural, no article is needed. If singular, proceed.
- Does the noun start with a vowel or a consonant? If a vowel, use "an." If a consonant, use "a". Note that some words that start with -u or -h have a consonant sound, which requires "a," and some have a vowel sound, which requires "an" (i.e. a hand, an hour, a university, an umbrella).