In Modern English, "Mood" describes the manner in which the action or state expressed by a verb is viewed with respect to its factuality, possibility, or command. Highly inflected languages, such as German and Japanese, typically possess numerous possible moods. English, a weakly inflected language, there are only three basic classes of mood: Indicative, Imperative, and Subjunctive.

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1.Indicative Mood states a fact or asks a question of fact. The indicative is, by far, the most commonly used mood.

Harry spends all of his money on comic books.

It’s simple enough: any statement related to a claim of fact is in the indicative mood. Mood is not affected if it is unlikely Harry actually spends all of his money on comic books; all that matters is that the verb usage is in the form of an assertion of fact.

How does Harry spend all of his money?

If we begin to answer the question—Harry spends all of his money on…-- we can see that it is inquiring into factuality in the same indicative sense as the previous sentence asserted factuality.

2. Imperative Mood expresses a command, request, or prohibition.

Spend all of your money on comic books!
Paul, please try to spend your money on something worthwhile.
Stop spending all of your money, boy.

Each sentence here illustrates a different shading of the imperative, but all of them issue a direct address in the second person. The basic bluntness and singular addressing relegate the imperative predominately to familiar speech and dialogue, but it can also be powerfully utilized in rhetoric (Ask not what your country can do for you, etc.).

3. The Subjunctive Mood is used chiefly to express the speaker’s attitude about the likelihood or factuality of a given situation. It has a present and past form.

A. The present subjunctive is most familiar to us in stock phrases such as God help him, be that as it may, come what may, and suffice it to say. It also occurs in "that" clauses used to state commands or to express intentions or necessity:

We demand that Paul stop spending all of his money on comic books.
It is necessary that Paul stop this behavior.

B. The past subjunctive is sometimes called the "were subjunctive", since were is the only subjunctive form that is distinct from the indicative past tense. It appears chiefly in
"if" clauses and in a few other constructions expressing hypothetical conditions:

If Paul were not spending all of his money, he would not be happy.
I wish Paul were not spending his money so recklessly.

These constructions might ring a bit funny and archaic to the ear, but, when used properly express subtleties of situation and condition that can sometimes be lost when the indicative is used.

B. Verb Tense

D. Voice