Mode is the manner in which the action, the being, or the state is asserted. Mode does not show the manner of the action or state, but the manner of its assertion. The action or state may be asserted:
• as something that may, can, or must take place.
• as something imagined or supposed which is placed under a condition. • as something desired.
In written English, the mode or manner of the action or state is expressed by means of limiting words. For example
The soldier fought (a reality) bravely (manner of the act). The soldier may fight (something imagined) bravely (manner of the supposed act).
The infinitive is not properly a mode of the verb. Since it does not assert action at all, it cannot be said to have any manner or mode of assertion. The same may be said of the participle. In fact, the infinitive is a participle, partaking of the properties of the noun and the verb, as the participle partakes of the properties of the adjective and the verb. There are five modes:
The indicative mode is the most common mode. It asserts a thing as actually existing. For example
James plays baseball.
William was struck.
Has he come?
The potential mode asserts the power, liberty, permission, necessity, or duty of acting, or of being in a certain state. For example
We can sing.
You may write.
Must he read?
They should obey the law.
Will you do it?
The subjunctive mode asserts a thing as conditional or as doubtful. For example
if he leave me
though he betray me
The imperative mode asserts a command, an entreaty, or a permission. For example
The infinitive represents the action or state as an abstract noun. For example
to be seen
The Indicative Mode
The indicative mode is used in principal propositions and is employed to represent what is actual, real, or absolute. It may be used in interrogative or exclamatory sentences. For example
Has he arrived?
The villain has burned the dwelling!
The indicative mode is often used in subordinate clauses, but it always represents what is. For example
I know that he discovered (actually) the plot.
The Potential Mode
The potential mode is also used in principal clauses however, a verb in the potential mode does not represent the actual. A verb in the potential mode represents that which exists or is supposed to exist only as an idea. The potential mode is used for those things that are merely imagined or thought of. For example
A storm may arise. (Actually there is no storm.)
Can he write?
How can you persist?
The ideal act or state of the potential mode, however, is supposed to have some relation to reality. The act or state indicated by the verb can become a reality. There is no impossibility in the way of its realization; no ability is wanting, and it may become a reality. This mode may be used ininterrogative, exclamatory, or strong supplicate sentences. For example
Can he leave the city in safety?
He may be assassinated.
May the truth be victorious!
The potential mode may be used in subordinate clauses, but always to represent what is ideal or what has not been realized. For example
He says that I may (I do not now) attend school.
The potential mode may be known by the auxiliaries may, can, must, might, could, would, and should.
The Subjunctive Mode
The subjunctive mode is used exclusively in subordinate clauses, and hence its name, submeaning under, and junco meaning I join. A subordinate clause is joined to the verb of the principal proposition by a subordinate conjunction. Subordinate conjunctions include including: • though
• except that
• save that
• provided that
These subordinate conjunctions impart the idea of doubt, contingency, or conditionality. Whatever of futurity may be implied in the subjunctive is to be accounted for...