Indo-European languages (of which English is one) use different forms of their verbs according to what is being expressed in the sentence. Specifically, the verb form will be different if:
- You are making an affirmation, a flat statement;
- You are making a demand, a suggestion, or issuing a command;
- You are expressing a doubt, a wish, hope, something hypothetical, or something contrary to fact.
The verb forms used for these three categories are called “moods” of the verbs. In grammar and logic, “mood” and “mode” are both used to refer to the state of mind of the speaker. Thus “mood” refers to the manner in which the thought is expressed.
- Affirmations and statements are made in the “indicative mood.” This is the form most often used, and you do not even have to think about it — it’s just about automatic. For example, “Joe drives too fast.”
- Commands, suggestions and demands are made in the “imperative mood.” Examples: “Do not drive too fast!” “I suggest/demand that Joe not drive too fast!“
- Uncertain or non-existent matters (doubts, wishes, hopes, hypothetical situations and anything contrary to fact) are expressed in the “subjunctive mood.” “If only Joe were a slower driver.“
Unlike the other Indo-European languages of Western Europe, English has not maintained a clear syntax for distinguishing these three moods. For example, if you were speaking French, there would be no doubt about your intention:
- to indicate something, or
- to command someone, or
- to express a desire.
The verb endings would tell the whole story. English, however, has abandoned most of its verb inflections, and with that, a clear way of telling another person which mood is being used. As an English speaker, you may not even be aware that you are expressing different syntactical moods as you move from affirmation to command to wish/desire/uncertainty/non-factual matter.
A few vestiges still remain, however. In expressing a condition contrary to fact, you must use the subjunctive. The present subjunctive of “to be” is “were.” This is a different “were” from the plural past tense form. For example, Tevye’s song in Fiddler on the Roof: “If I were a rich man, all day long I’d biddy biddy bum, if I were a wealthy man. ” Notice that it is not “I was” or “I am.” It’s “I were.” That is the present subjunctive.
In Gilbert & Sullivan’s Pirates of Penzance, Frederic (the hero) asks of a group of lovely maidens on the shore if perhaps one of them would rescue him from his fate as an apprentice to pirates. He sings, “I swear by heaven’s high arch above you, if you will cast your eyes on me, however plain you be, I’ll love you.” That is the future subjunctive: “You be.”
The reason that you, as an English-speaker, may find this business of “moods” rather astonishing is that English has gradually replaced the subjunctive and the imperative forms with what are called “modal verbs”: can/could, may/might, must, will/would, and shall/should. To express a command, demand or suggestion, for example, we use “must,” “ought to” or “should.” To express doubt or uncertainty, we use “may” or “might.” To express hypothetical actions or conditions, we use “would.” These are auxiliary verbs that do the work for the main verb, so that the special imperative and subjunctive forms become unnecessary. Note that the adjective “modal” is used in the same sense as the noun “mood” to describe the state of mind of the speaker.
This evolution away from subjunctive forms does not mean, however, that the subjunctive is extinct or vestigial. No, it is still wrong, that is, bad grammar, to say “If I was you . . . ” or “He reacted as if she has two heads.”(It should be: “If I were you . . . ” and “He reacted as if she had two heads.“)
As a general matter, remember that “were” is the correct form of “to be” to express the subjunctive in the present. (She looked as if she were ten feet tall.) In the past, use “had been.” (“If only the Lone Ranger had been here!” — note that it is not “has been.“) For the future, use “be.” This will feel more natural if you use “may” or “might” with it. (“Who be you?“; “Who might you be?”)
For imperatives, “be” is also the correct form, as in “Be quiet!”
That covers almost all of the “mood” issues that otherwise can be handled by the modal verbs.