When a verb is preceded by a word that expresses a condition, doubt, motive, wish, or supposition, it is in the SUBJUNCTIVE MOOD; as, “If he study, he will improve; I will respect him, though he chide me; He will not be pardoned, unless he repent; Had_ he been there, he would have conquered;” (that is, if he had been there.)

The conjunctions if, though, unless, in the preceding examples, express condition, doubt, &c.; therefore, the verbs study, chide, repent, and had been, are in the subjunctive mood.

NOTE 1.  A verb in this mood is generally attended by another verb in some other mood.  You observe, that each of the first three of the preceding examples, contains a verb in the indicative mood, and the fourth, a verb in the potential.

2.  Whenever the conjunctions if, though, unless, except, whether, lest, or any others, denote contingency or doubt, the verbs that follow them are in the subjunctive mood; as, “If he ride out every day, his health will probably improve;” that is, if he shall or should ride out hereafter.  But when these conjunctions do not imply doubt, &c. the verbs that follow them are in the indicative, or some other mood; as, “Though he rides out daily, his health is no better.”  The conjunctive and indicative forms of this mood, are explained in the conjugation of the verb to love.  See page.

The IMPERATIVE MOOD is used for commanding, exhorting, entreating, or permitting; as, "Depart thou; Remember my admonitions; Tarry awhile longer; Go in peace.”

The verb depart expresses a command; remember exhorts; tarry expresses entreaty; and go, permission; therefore they are all in the imperative mood.

The imperative, from impero, to command, is literally that mood of the verb used in commanding; but its technical meaning in grammar is extended to the use of the verb in exhorting, entreating, and permitting.

A verb in the imperative mood, is always of the second person, though never varied in its terminations, agreeing with thou, ye, or you, either expressed or implied.  You may know a verb in this mood by the sense; recollect, however, that the nominative is always second person, and frequently understood; as, George, give me my hat; that is, give thou, or give you.  When the nominative is expressed, it is generally placed after the verb; as, Go thou; Depart ye; or between the auxiliary and the verb; as, Do thou go; Do ye depart. (Do is the auxiliary.)

The POTENTIAL MOOD implies possibility, liberty, or necessity, power, will, or obligation; as, “It may rain; He may go or stay; We must eat and drink; I can ride; He would walk; They should learn.”