Irregular verb forms are one of the most difficult grammar topics to grasp, even for native speakers, many of whom use incorrect irregular forms unconsciously. Second, according to Grammarly's study, run-on sentences are among the most common grammar errors made by writers around the world. Third, because English does not conjugate verbs to represent the subject's gender, you simply need to pay strict attention to the subject's number. Finally, when you employ the pronouns "her" or "him," readers must know to whom you are referring. An ambiguous pronoun is one that lacks a clear antecedent.