The imperative mood is used to express commands. Positive commands in English take the form of the base form of the verb: “Give me a wrench.” “Clean your room.” “Read this report, then give it to the supervisor.” “Send us your address.” Negative commands are formed with “Don't” + BASE VERB FORM. “Don't call me at work.” “Don't be late.” “Don't forget your lunch.” It is important to remember that there are only a few acceptable situations to use the command form in, such as talking to children, to your students, when giving instructions, etc. Otherwise, it is more polite to request people to do things, using modals such as “would,” “could,” “will” and “can”: “Could you give me a wrench, please?” “Will you please clean your room?” “Would you read this report, then give it to your supervisor?” “Can you send us your e-mail address?” The subjunctive mood is used to express emotion, doubt, desire and possibility. It has mostly disappeared in English, though it is very important in other European languages. Even educated speakers of English do not regularly use the subjunctive correctly. “If I were (not “was”) a rich man, I'd travel all over the world.” “If she were (not “was”) any taller, she'd be taller than her husband.” The subjunctive also occurs in clauses with the verb “wish”: “I wish I were (not “was”) in California.” The subjunctive mood is used in object complements where the verb in the main clause is a verb like “suggest,” “recommend,” “demand,” “ask,” etc.: “I suggest that he take (not “takes”) the day off.” “I demand that all employees be (not “are”) here on time.” “They asked that we sing in the choir.” (“Sing” has the same form in the subjunctive as it is in the indicative mood. Most verbs in the subjunctive mood are only recognizable in the third person singular. “We” is first person plural. “Be” is the only exception.) The subjunctive mood is also expressed in sentences beginning with “It is important that...”: “It is important that you be (not “are”) ready for an emergency.” “It is very important that I be (not “am”) prepared for the presentation.” Finally, the subjunctive mood is still used in established or idiomatic expressions, such as “(May) God bless you,” “So be it,” “(May) God be with you,” etc.
In English, there are three “moods.” A mood is a way of using a verb to show the attitude of the speaker toward what he is saying. The Indicative mood expresses facts. All the tenses discussed in the Grammar Corner, Verb Tense section are in the indicative mood. The other two moods are the imperative mood and the subjunctive moods.