Difference between (a, the)

A child ran across a street. You don't know this child and hasn't been mentioned until now.

The child ran across the street. You know this child or he has been mentioned already. Thus, he is a specific child.

Thank you,

But,

I don't understand your explanations. [You don't mention about street (a street, the street)]

A child ran across a street.

The child ran across the street.

The child ran across a street.

A child ran across the street.

Please explain me the exact meaning of the sentences.

Super Sonic wrote:

Nmurugeshan2nev wrote: Thank you, But, I don't understand your explanations. [You don't mention about street (a street, the street)] A child ran across a street. The child ran across the street. The child ran across a street. A child ran across the street. Please explain me the exact meaning of the sentences. A child ran across a street. (You neither know the child nor the street (By the way, as you can see, I used "the" both before "child" and "street", as they were taken out of your sentence.)) The child ran across the street. (You know which child ran across which street.) The child ran across a street. (You know the child, but you don't know which street s/he ran across.) A child ran across the street. (You don't know the child, but you know which street s/he ran across.) Hope I was of service.

Now, I understand

Thank you very much.