1. Subject-Verb Agreement Errors The subject and verb of a sentence must agree with one another in number whether they are singular or plural. If the subject of the sentence is singular, its verb must also be singular; and if the subject is plural, the verb must also be plural. 2. Sentence Fragments Sentence fragments are incomplete sentences that don’t have one independent clause. A fragment may lack a subject, a complete verb, or both. Sometimes fragments depend on the proceeding sentence to give it meaning. 3. Missing Comma After Introductory Element A comma should be used after an introductory word, phrase, or clause. This gives the reader a slight pause after an introductory element and often can help avoid confusion. 4. No Comma In A Compound Sentence A comma separates two or more independent clauses in a compound sentence separated by a conjunction. The comma goes after the first clause and before the coordinating conjunction that separates the clauses.