How to use the articles? A book is something you read

[Romashka]

Could somebody explain me more clearly differents between two cases..

We use indefinite "a/an" before a singular countable noun which is used as an example of a class of things.
"A book is something you read."

And we use defeinite "the" before singular nouns used to represent a class of objects.
"The donkey is a very obstinate animal."

I a little bit mixed up.. Thank you..

[Martino]

Hi Romashka,

You use "the" when referring to a particular object/person/thing. You use "a/an" when talking about a member of a group.

[Inga]

This is my vision :):
a (though it is used in many different situations) in your question can be used to give a definition: 'What is a donkey?' - 'A donkey is a grey or brown animal like a horse, but smaller and with long ears.'
To refer to the whole group you say 'donkeys' like in 'The rugged terrain is inhabited by deer, antelopes and, locals say, wild donkeys.'
In academic or formal language, mainly to describe typical characteristics, the is used : 'Smaller than the horse, the domestic donkey and African wild ass stand about 1.25 m (about 4.1 ft) high at the shoulder.[/b]
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[Romashka]

Thank you Inga and Martino.. But I still do not sure, for example why can't I say: "A donkey is a very obstinate animal" ?

[Alan]

Hi Romashka,

You can indeed say: A donkey is a very obstinate animal. Here you are talking in general terms. If you use 'The donkey', you are picking out 'donkey' from all other animals.

You might like to read something I've written for the site on articles: http://www.english-test.net/lessons/57/index.html You can then continue with (2) (3) and (4).

Alan
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English as a Second Language
You can read my ESL story Present Simple

[Romashka]

Thank you very much Alan! I didn't thought before how can articles changes the colour of sentence.