Cambridge Grammar of English Hardback with cd-rom a comprehensive Guide

Verb phrases: mood

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The verb phrase also expresses contrasts of mood. Mood refers to the factual or

non-factual status of events. Non-factual here means events which do not happen

or are only desired. The moods of English are indicative, imperative and

subjunctive.

The indicative is a factual mood. It is by far the most frequent mood, and

involves all the choices of person, tense, number, aspect, modality and voice

discussed above:

I

’ll give you a call in the week.

We 

were talking about this the other day.

The imperative mood is a non-factual mood and is used to issue directives. It

involves the base form of the verb:

Sign here, please.

Just 

leave it on the table.

The subjunctive mood is a non-factual mood and is very rare in English. It refers

to wishes, desires, etc. It is used after a very limited number of verbs (e.g. suggest,

insist

, recommend, demand), occasionally after conditional subordinators (e.g. if,

lest

, on condition that, whether) and occasionally after expressions of necessity

(e.g. it is important/imperative/essential that).