This document discusses sentence structure and the different types of sentences. It begins by defining the basic units of language - letters, words, phrases. A sentence is defined as a group of words that conveys meaning. There are four main types of sentences: simple sentences contain one independent clause; compound sentences contain two independent clauses joined with a conjunction; complex sentences contain one independent and one dependent clause; and compound-complex sentences contain one dependent clause and two or more independent clauses. Examples are provided to illustrate each sentence type. The document concludes with exercises to identify the type of different sentences.