Subject-verb agreement can be a tricky and confusing aspect of grammar, but it is essential to ensure clear communication and effective writing. In particular, knowing when to use “do” as the auxiliary verb can be challenging, so let`s delve deeper into this topic.

First, let`s define what we mean by “auxiliary verb.” An auxiliary verb, also known as a helping verb, is used in conjunction with a main verb to create verb tenses, voice, and mood. Common auxiliary verbs include “be,” “have,” and “do.”

When it comes to subject-verb agreement, the auxiliary verb must agree with the subject in terms of both tense and number. For example, in the present tense, we use “do” as the auxiliary verb for plural subjects and “does” for singular subjects. Let`s take a look at some examples:

– They do their homework every day.

– She does her homework every day.

In the above examples, “do” agrees with the plural subject “they,” and “does” agrees with the singular subject “she.”

However, it`s important to note that there are certain cases where “do” is not used as the auxiliary verb, even with plural subjects. This typically occurs when the main verb is a form of “to be.” For example:

– They are happy with their grades.

In this case, “are” is the main verb and does not require “do” as the auxiliary verb, even with a plural subject.

Another aspect to consider is when to use “do” as the main verb, rather than as an auxiliary verb. In this case, “do” is typically used to form questions and negatives in the present tense. For example:

– Do they study every day?

– They don`t study every day.

In the first example, “do” is used to form the question, and in the second example, it is used with “not” to form the negative.

In summary, knowing when to use “do” as the auxiliary verb is important for subject-verb agreement in the present tense. It should agree with the subject in terms of both tense and number. Additionally, it`s important to understand when “do” is not used as the auxiliary verb, such as with a main verb that is a form of “to be.” Finally, “do” can also function as the main verb in questions and negatives in the present tense. By mastering these rules, you can improve your writing and ensure clear communication.