The building collapsed. (intransitive)
The monster collapsed the building by sitting on it. (transitive)
Second, quite a few verbs require not only one, but two objects: one called direct object, and the other indirect object. Verbs requiring both indirect and direct objects are called distributive verbs[1].
If a verb is used as the main verb of a sentence or a clause, that is, it makes an assertion about or expresses a state of being of its subject, then it is called a finite verb (let's call it a predicate[2] verb of a clause or sentence):
The truck demolished the restaurant.
Verbals
When a verb is not used as the predicate verb of a clause or a sentence, then it is called non-finite verb. Three major forms of non-finite verbs are gerund, participle (present and past participles), and infinitive. Another name for non-finite verbs is called verbal.
Four Basic Forms of a Verb
Fortunately, the inflections (endings) of English verb forms are not difficult to remember. There are only four basic forms: base form (looks same as bare infinitive, i.e., without the infinitive article to), past form, present participle, and past participle[3].
Instead of forming complex tense forms with endings, English uses auxiliary verb forms. For instance, English does not have a proper ending for future forms; we use auxiliaries such as "I am going to read this afternoon", or "I will read", or even "I am reading this book tomorrow".
Linking Verbs
A linking verb connects a subject and its complement. A linking verb is also called "copula". The verb "to be" is the first linking verb; other linking verbs are ones related to the five senses of human bodily feelings (look, sound, smell, feel, and taste); still others are ones that reflect a state of being (appear, seem, become, grow, turn, prove, remain). What follows the linking verb will be either a noun complement or an adjective complement. Examples:
Those professors are stupid;
I feel great;
Have you studied Latin? From Latin we know that the complement of a linking verb must take the nominative case (Latin calls it predicate nominative); that is, the complement must take the same form as the subject. With such a understanding, we should say that "It's us" is a grammatically wrong sentence. The correct one is "It's we", because "us" is the accusative case that an object should take and "we" is the nominative case that can be used as a predicate. By the same reasoning, "It's me", "It's him", "It's her", and "It's them" are all wrong sentences since these pronouns are all in the accusative case but they are not objects in these sentences. Therefore, they should be corrected as "It's I", "It's he", "It's she", and "It's they"[4].
Finally, there are another handful of verbs that reflect a change in state of being and are sometimes called resulting copula (linking verbs)[5].
His face turned red;
She became older;
The milk has gone sour;
Active and Passive Voice
Verbs can be expressed in different voices and English has two of them: active and passive. This is a big topic that justifies a separate section of note.
Mood
Mood in verbs refers to one of three attitudes (you can call it emotions if you like) whoever expresses the verb holds (indicative, imperative, and subjunctive). The indicative mood is used to make a statement or ask a question; and it is most used by all of us. The imperative mood is used when we are feeling sort of bossish and want to give a directive, a strong suggestion, or an order:
Get your homework done before you play X-box[6].
P
Get out of town.
Note that no subject is shown in these imperative sentences and the pronouns "you" is the understood subject (the second person pronoun, singular or plural, depending on context), except in this kind of imperative sentences "Let's work on these issues now", in which the subject is "we", the first person pronoun plural.
The subjunctive mood is mostly used in dependent clauses that do the following: 1) express a wish; 2) begin with "if" and express a condition that does not exist or is contrary to the fact; 3) begin with "as if" and "as though" when such a clause describes a speculation or condition contrary to fact; and 4) begin with "that" and express a demand, requirement, request, or suggestion[7]. Examples:
If Juan were more aggressive, he’d be a better hockey player.
The subjunctive mood is not as important in English as it is in other languages, like Latin, French and Spanish, which happen to be more subtle and discriminating in hypothetical, doubtful, or wishful expressions. Many situations which would require the subjunctive in other languages are satisfied by use of one of the several auxiliary verbs in English.
The words "if", "as if", or "as though" do not always signal the subjunctive mood. If the information in such a clause points out a condition that is or was probable or likely, the verb should be in the indicative mood. The indicative tells the reader that the information in the dependent clause could possibly be true. P
Verbs like "demand", "require" and "suggest" in the main clause requires the subjunctive use of only the base form of the verb in the subjunctive dependent clause:
He demands that his students use two-inch margins when printing term papers.
She suggests that we be on time tomorrow.
Also, in the sentence structure "it is great (or possible, ideal, nice, necessary) that …", the verb in the dependent clause needs to be in the base form, too.
It is great that he leave this afternoon.
The past tense of the subjunctive has the same forms as the indicative past tense except for the verb "to be", which uses "were" regardless of the number of the subject.
Auxiliary or Helping Verbs
Also a separate section of notes on both Auxiliary Verbs and Modal Auxiliaries will be done soon. See these notes.