Articles

(1) The Definite Article ("The")

• "The" is called the definite article.
• It defines its noun as something specific
• (e.g., something previously mentioned or known, something unique, something being identified by the speaker).
• This is the lake. (This is a previously specified lake, i.e., one already known to the readers.)

(2) The Indefinite Article ("A" or "An").

• "A" and "an" are called the indefinite articles.
• They define their noun as something unspecific
• (e.g., something generic, something mentioned for the first time).
• This is a lake. (This is a previously unspecified lake.)

Examples:

• I fell over the chair again. (The chair is specific. It is known to the audience.)
• Can you pass me a chair? (This means an unspecific chair, i.e., any chair.)
• I loved the apple pie after the meal. (In this example, the audience knows which apple pie is being praised, e.g., the one at last night's dinner.)
• I love an apple pie after dinner. (The audience understands that the speaker likes to eat an apple pie after dinner (any apple pie will do).

"An" is used before a vowel sound, and "a" is used before a consonant sound. The word sound is important because consonants can create vowel sounds, and vowels can create consonant sounds. Therefore, the use of "an" or "a" is determined by the sound not the letter. Look at these examples:

• A house 
  
• An hour 
  
  ("House" and "hour" start with the same three letters; however, "house" attracts "a," and "hour" attracts "an." This is because "house" starts with a consonant sound, but "hour" starts with a vowel sound.)
• A uniform row 
  
• An unidentified man 
  
  ("Uniform" and "unidentified" start with the same three letters; however, "uniform " attracts "a," and "unidentified" attracts "an." This is because "uniform" starts with a consonant sound ("yoo"), but "unidentified" starts with a vowel sound.)

Be especially careful with abbreviations:

• An MOT 
  
  (The letter "em" starts with a vowel sound.)
• An LRS 
  
  (The letter "el" starts with a vowel sound.)
• A US diplomat 
  
  (The letter "yoo" starts with a consonant sound.)

Articles Go before Adjectives

An article often modifies a noun that is already being modified by an adjective. When this happens, the article goes before the adjective (or adjectives). For example:

• Please open the small box first. (Here, the noun "box" is being modified by the adjective "small." The definite article "the" sits before the adjective. Remember that the use of "the" tells us that we are talking about a box already known to the audience.)
• You will get an excellent pizza at Papa Antonio's. (Here, the indefinite article "an" sits before the adjective "excellent.")

Indefinite Articles Are Used with Singular Nouns*

The indefinite article ("a," "an") is only for singular nouns. It is not used for plural nouns.

As the indefinite article specifies one thing (e.g., "a cup" means "one cup"), it is not used with non-countable nouns (e.g., "water," "air," "integrity"). For example:

• I need an air. 
  
• Play me a music. 
  
• Give me a heat. 
  

Articles Are Not Used with Possessive Determiners or Possessive Pronouns

Articles are not used with possessive determiners ("my," "your," "his," "her," "its," "our," "their") or possessive pronouns ("mine," "yours," "his," "hers," "ours," "theirs") as these already show that something is specific. For example:

• Take me to the your leader. 

  

• Take me to your leader. 

  

• Can I borrow a yours? 

  

• Can I borrow yours? 

  
  [Grammar Monster](Articles: Definition and Examples (grammar-monster.com))