Sometimes simple questions are not so simple. If I asked what the verb elected means in the clause the board elected her president, few of us would hesitate long in saying chosen by vote, or selected, or even just made. But if I then said that she was president for two years, how exactly would we define the verb was? What, in other words, does it mean to be? (Mercifully, I’m asking that question grammatically, not philosophically.)
Let’s step back and remind ourselves that verbs can be organized into three large groups: transitive, intransitive, and linking. A verb, of course, shows what the subject of a clause is doing, and when a subject is acting in such a way that it is directly affecting something else, then that verb is called transitive and what is being affected is called the direct object. We would therefore say that the verb elected in our example is transitive and its direct object is the pronoun her. By contrast, verbs of action which do not have a direct object are called intransitive. In the sentence the board deliberated for an hour, the subject board did not deliberate anything, it just deliberated; there is no direct object, and so here the verb is intransitive. The same verb can very often be used transitively or intransitively, sometimes with a change in meaning; any standard university-level dictionary will reliably advise (or could I have written advise you? Check the dictionary).
Not all verbs, though, indicate an action, whether transitive or intransitive. Some serve simply to associate the subject with its predicate, that part of a clause which is saying something about the subject. Such verbs are called linking, or copulative (a copula in Latin is a rope or link or leash), and the chief copulative verb in English is be. The word be can strike us sometimes as odd (to say nothing of the even more peculiar word being) because we forget that it is merely the first of the three principal parts of the verb be, was, been. Almost all verbs have three principal parts, and they are listed in the order of infinitive, simple past tense, and past participle. So the verb was in our second example is the simple past tense of the verb be.
In that sentence, though, the verb was does nothing more than bring the subject she alongside the noun president. The two, in other words, are to be identified as the same thing, one not acting on the other, but she living and being the president herself. Because the two are not different, we cannot say that president is the direct object of was; instead, it is called a predicate noun, and that term serves to remind us that a copulative verb merely asserts identity, not action. All of this becomes quite practical in revision, where we are well advised to prefer verbs of action over verbs of identity, or what is called state of being. Too many verbs of state at the expense of verbs of action will weaken the fiber of a paragraph.
So to be can mean to have identity as something else. But then there is a sentence like this: She was here yesterday. If we look closely, there is no noun in the predicate with which the verb was can identify the subject she; the noun yesterday indicates time, so in this sentence it is an adverb, and adverbs (also like the word here) are relations, not things (to say nothing of the fact that identifying she with yesterday would make little logical sense). So if the verb was in this example is not a linking verb, what is it doing? It means, in fact, to exist, not to have identity as, and so we must categorize it as an intransitive verb, a verb of action without a direct object. Strange to say, but simply to be is to act, and so it is that grammar can take us to the edge of philosophy.