Mood is a grammatical category which indicates the attitude of the speaker towards the action expressed by the verb from the point of view of its reality. There are 3 moods: the imperative( order), the indicative( fact) and the subjunctive mood(hypothesis).
Modality - verbs which help you to express need, possibility, ability, necessity, advice etc.
Grammatical means: modal verbs.
Lexical means: modal verbs expressing -
- certainly - surely, certainly, of course, absolutely
- supposition - perhaps, possibly, maybe, probably
- whether the speaker considers the action desirable or undesirable - happy, perfectly, naturally, actually, luckily, basically