A sentence is a grammatical unit that is composed of one or more clauses.
kinds of sentences:
A complex sentence is a sentence which includes
* at least one main clause, and
* at least one subordinate clause.
# The man whom you see is my brother.
A compound sentence is a sentence composed of two or more coordinate clauses.
Fragments are incomplete sentences. Usually, fragments are pieces of sentences that have become disconnected from the main clause. One of the easiest ways to correct them is to remove the period between the fragment and the main clause. Other kinds of punctuation may be needed for the newly combined sentence.