A word (one of the parts of speech and a member of a closed word class) that shows the relationship between a noun or pronoun and other words in a sentence.
 Such as - to, in, on, for, from, of, between,among etc.
Example-
Along-

We walked along the road.
trees grew along the river bank.

Across-
They built a bridge across a river.
The thief ran across the field.

Through-
The thief came through the window.

By-

Ram will return by 4 p.m.
She is sitting by her mother.
The book is written by a famous writer.
I may come by bus.
He came in by the back door.

With -

I beat him with a stick.
He went to bazar with his wife.

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