1. Subject-Verb Agreement: This error occurs when the verb in a sentence does not agree with the subject in number. For example: "The dog run in the park." (incorrect) vs. "The dog runs in the park." (correct)
2. Pronoun Agreement: This error happens when a pronoun does not agree with its antecedent (the noun it refers to) in number, gender, or person. For example: "The cat it sat on the mat." (incorrect) vs. "The cat it sat on the mat." (correct)
3. Run-on Sentences: This error occurs when two or more independent clauses (clauses that can stand alone as sentences) are joined together without proper punctuation or conjunctions. For example: "The cat chased the mouse the mouse ran away." (incorrect) vs. "The cat chased the mouse, and the mouse ran away." (correct)
These are just three of the many common sentence errors. Other common errors include misplaced modifiers, comma splices, and fragments.