Definite articl & Indefinite article

Definite article

A definite article indicates that its noun is a particular one (or ones) identifiable to the listener. It may be something that the speaker has already mentioned, or it may be something uniquely specified. The definite article in English, for both singular and plural nouns, is the.

The children know the fastest way home.

The sentence above refers to specific children and a specific way home; it contrasts with the much more general observation that:

Children know the fastest way home.

The latter sentence refers to children in general, perhaps all or most of them. Likewise,

Give me the book.

refers to a specific book whose identity is known or obvious to the listener; as such it has a markedly different meaning from

Give me a book.

which does not specify what book is to be given. The definite article can also be used in English to indicate a specific class among other classes:

The cabbage white butterfly lays its eggs on members of the Brassica genus.

The definite article is sometimes also used with proper names, which are already specified by definition (there is just one of them). For example: the Amazon, the Hebrides. In these cases, the definite article is strictly speaking superfluous. Some languages also use definite articles with personal names. For example, such use is standard in Portuguese: a Maria, literally: "the Maria". It also occurs colloquially in Spanish, German and other languages, and is sometimes heard in Italian. In Hungary it is considered to be Germanism.

Indefinite article

An indefinite article indicates that its noun is not a particular one (or ones) identifiable to the listener. It may be something that the speaker is mentioning for the first time, or its precise identity may be irrelevant or hypothetical, or the speaker may be making a general statement about any such thing. English uses a/an, from the Old English forms of the number 'one', as its primary indefinite article. The form an is used before words that begin with a vowel sound (even if spelled with an initial consonant, as in an hour), and a before words that begin with a consonant sound (even if spelled with a vowel, as in a European).

She had a house so large that an elephant would get lost without a map.

Before some words beginning with a pronounced (not silent) h in an unstressed first syllable, such as hallucination, hilarious, historic(al), horrendous, and horrific, some (especially older) British writers prefer to use an over a (an historical event, etc.).^[3] An is also preferred before hotel by some writers of British English (probably reflecting the relatively recent adoption of the word from French, where the h is not pronounced).^[4] The use of "an" before words beginning with an unstressed "h" is more common generally in British English than American.^[4] American writers normally use a in all these cases, although there are occasional uses of an historic(al) in American English.^[5] According to the New Oxford Dictionary of English, such use is increasingly rare in British English too.^[3] Unlike British English, American English typically uses an before herb, since the h in this word is silent for most Americans. The correct usage in respect of the term "hereditary peer" was the subject of an amendment debated in the UK Parliament.^[6]
The word some is used as a functional plural of a/an. "An apple" never means more than one apple. "Give me some apples" indicates more than one is desired but without specifying a quantity. This finds comparison in Spanish, where the singular indefinite article 'un/una' ("one") is completely indistinguishable from the unit number, except where it has a plural form ('unos/unas'): Dame una manzana" ("Give me an apple") > "Dame unas manzanas" ("Give me some apples"). However, some also serves as a quantifier rather than as a plural article, as in "There are some apples there, but not many."
Some also serves as a singular indefinite article, as in "There is some person on the porch". This usage differs from the usage of a(n) in that some indicates that the identity of the noun is unknown to both the listener and the speaker, while a(n) indicates that the identity is unknown to the listener without specifying whether or not it is known to the speaker. Thus There is some person on the porch indicates indefiniteness to both the listener and the speaker, while There is a person on the porch indicates indefiniteness to the listener but gives no information as to whether the speaker knows the person's identity