A main verb is the word in a sentence that indicates the action being performed by the subject. This may be accompanied by additional verbs, typically those referred to as auxiliary or modal, but it is the main one that actually shows what is happening. In a sentence like "The cat ran to the window," the word "ran" is a main verb that shows what action was performed by the subject, "The cat;" "to the window" is a prepositional phrase that gives additional information about that action. While this example has no other verbs, a sentence like "I am going to the store," has both "am" and "going;" the main verb is "going" and "am" is an auxiliary verb.
Sentences, or clauses, typically consist of two major elements, which are the subject and the predicate. The subject is what the sentence is about, typically a noun that presents the person or thing that is taking action. Everything else in a sentence or clause is the predicate, which provides additional information about that subject. The main verb is part of the predicate, telling the reader or listener what action is being performed.
A simple example is the sentence "The man threw the ball." "The man," is the subject of the sentence and the predicate consists of "threw the ball." "Threw" is the main verb in this sentence, as it provides the direct information about the action being performed by the subject. The rest of the predicate, "the ball" is a noun phrase that acts as the direct object, which indicates what the action of the main verb is being performed upon.
More complex sentences often have additional verbs, which can provide more information through various means. An auxiliary verb is often used with a main verb to change its tense or provide additional meaning. For example, in the sentence "I do not like ham," the subject is "I" and "ham" is the direct object. "Like" is the main verb, as it indicates the action of the subject, but the word "do" is also a verb. In this case, it is an auxiliary verb that is used with "not" to indicate that the sentence is a negative statement.
Auxiliary verbs can also be used to change a sentence to perfect tense. The sentence "I walked to school yesterday" is in the past tense, while "I have walked to school many times" is perfect tense. This is created through the addition of the auxiliary verb "have" to the main verb "walked."
There are also modal verbs that are used to indicate ability to do something or otherwise provide additional information about the main one. For example, in the sentence "I can walk to school tomorrow," the word "can" is a modal verb that indicates the ability of the subject to perform the action. Similar modals include words like "must" and "should," which indicate whether or not actions are recommended.