Many languages have the concept of grammatical mood, which describes the speaker's relation to reality or intent in speaking. Many languages express distinctions of mood by inflection of the verb. Because Modern English does not have all of the moods described below and has a very simplified system of verb inflection as well, it is not straightforward to explain the moods in this language. Note too that the exact sense of the moods differ from language to language.
Possible moods include indicative, imperative, subjunctive, injunctive, and optative.
The indicative mood express facts and opinions. It is the most commonly used mood and is found in all languages. Example: "Paul is reading".
The imperative mood expresses commands, direct requests, prohibitions. In many circumstances, directly using the imperative mood seems blunt or even rude, so use with care. Example: "Paul, read that book".
The subjunctive mood has several uses in dependent clauses, when discussing hypothetical or unlikely events, or for polite requests. A subjunctive mood exists in English but many native English speakers have not mastered it. Example: "If Paul were reading the book, he would be occupied". Paul is not in fact reading.
The subjunctive mood figures prominently in the grammar of the Romance languages, which require this mood for certain types of dependent clauses. This point commonly causes difficulty for English speakers learning these languages.
The optative mood expresses hopes or wishes and has other uses that may overlap with the subjunctive mood. Few languages have an optative as a distinct mood; Ancient Greek and Sanskrit are two that do. Example: an ancient Greek might say "Would that Paul would read more!" with the words would that expressed by the placing the verb read in the optative mood.