Subject-verb agreement is one of the most important aspects of grammar that every good writer must master. The use of “has” and “had” is essential in determining the right form of a verb to use in a sentence. As a professional, I cannot overemphasize the importance of getting this aspect of grammar right, especially when writing for online platforms that require good search engine optimization.

“Has” is a form of the verb “to have” that is used with singular subjects in the present tense. For example, “He has a great sense of humor.” In this case, “has” agrees with the singular subject “he.” Similarly, “she has a new car” is correct, while “she have a new car” is incorrect because “have” is not the correct verb form for the singular subject.

On the other hand, “had” is the past tense form of “to have” and is used to indicate an action that took place in the past. For example, “He had a great time at the party.” In this sentence, “had” refers to the past tense of the verb “to have” and agrees with the singular subject “he.” Similarly, “She had a great trip to the beach” is correct, while “She has a great trip to the beach” is incorrect because “has” is incorrect verb form for a past event.

It is not uncommon to find errors in subject-verb agreement, specifically with the usage of “has” and “had.” These errors can often be identified by simply checking the subject and the verb to ensure that they agree in tense. For instance, “The dog has chased the cat” is correct because “dog” is a singular subject and “has” is the correct verb form. However, “The dog have chased the cat” is incorrect because “have” is the incorrect verb form for a singular subject.

Another common mistake in subject-verb agreement is using “has” when “had” is required in the sentence. For example, “She has visited Paris last year” is incorrect because “had” which refers to past tense should be used instead. The correct sentence should be “She had visited Paris last year.”

In summary, mastering subject-verb agreement is very crucial in effective communication, especially in writing. As a professional, I often come across many errors in this aspect of grammar that can negatively impact the quality of a piece of writing. Therefore, it is essential to always keep in mind the rules of subject-verb agreement and use the correct verb form that agrees with the subject and tense of the sentence.