Judging by comments I’ve read on this and other language sites, many people are not quite clear as to the difference between the grammatical terms mood and tense. For example, I’ve seen such expressions as “subjunctive tense” and “progressive mood.”
Because both tense and mood have to do with verbs, the confused terminology is understandable. Tense, however, refers to time, whereas mood refers to manner of expression.
The three possible divisions of time are past, present, and future. For each, there is a corresponding verb tense:
Present: He walks now.
Past: Yesterday he walked.
Future: Tomorrow he will walk.
Each of these tenses has a corresponding complete tense: perfect, past perfect (pluperfect), and future perfect:
Perfect: He has walked every morning since Monday.
Past Perfect: He had walked a mile by the time we joined him.
Future Perfect: By tomorrow, he will have walked twenty miles.
Each of these tenses has a continuous or progressive form:
Present Continuous: I am still walking.
Past Continuous: I was still walking when you phoned.
Future Continuous: I shall/will be walking when you reach town.
Perfect Continuous: I have been walking since early morning.
Past Perfect Continuous: I had been walking for an hour when you phoned.
Future Perfect Continuous: When you see me, I shall have been walking for six hours.
Mood is the form of the verb that shows the mode or manner in which a thought is expressed. Mood distinguishes between an assertion, a wish, or a command. The corresponding moods are: Indicative (assertion), Subjunctive (wish), and Imperative (command).
Note: Unlike some languages, English does not have an “Interrogative Mood”; questions are formed by changing word order and not by altering the verb.
The word indicative derives from Latin indicare, “to declare or state.” Indicative Mood expresses an assertion, denial, or question about something:
Assertion: I liked him very much before he did that.
Denial: He is not going to remain on my list of friends.
Question: Will you continue to see him?
The word imperative derives from Latin imperare, “to command.” Imperative Mood expresses command, prohibition, entreaty, or advice:
Command: Go thou and do likewise.
Prohibition: Stay out of Mr. MacGregor’s garden!
Entreaty: Remember us in your prayers.
Advice: Beware of the dog.
The “true subjunctive” equivalent to the Latin Optative Mood (opare, “to wish”) is rare in modern English. Examples of the “true” subjunctive: “If I were king,” “God save the Queen!”
In most contexts dealing with unreal situations, speakers used a mixed subjunctive. The use of the auxiliaries may, might, should, and would creates a mixed subjunctive in which one verb is in subjunctive and another in indicative mood:
If I should see him, I will tell him.
He came that they might have life.
According to the Penguin Dictionary of English Grammar,
The distinctive subjunctive forms are now confined to the verb be and to the third-singular forms of other verbs; they are still common in American English, while in British English they are confined to very formal styles.
In American English, the subjunctive often occurs with the following verbs:
suggest: I suggest that she refuse his offer.
demand: They are demanding that he go to London for an interview.
propose: The father proposed that his son be locked up to teach him a lesson.
insist: We all insisted that he accept treatment.
British usage tends to use should in such constructions: I suggest that she should refuse his offer.