The Four Humours

The four humours were part of a theory of personality which used to account for temperament. They were conceived of as fluids which, when present in the correct proportions, produced a sound individual. If one were too predominant, the person would have an excess of that quality. They were:
blood - hot and moist, giving rise to a sanguine outlook, optimistic, sociable and cheerful
yellow bile or choler - hot and dry, promoting a tendency to anger and excitability
phlegm - cold and moist, evident in an unemotional, thoughtful, even sluggish, person
black bile or melancholy - cold and dry in one given to gloom and introversion
It is important to be aware of this hypothesis when reading texts of the Middle Ages and the Elizabethan era as it underlies some of them: for example Hamlet might have been immediately recognised as melancholic without too much need for further explanation.
The idea is not completely dead as we may still refer to a person as sanguine, phlegmatic or choleric

PERSONA

This word, which in Latin means an actor's mask, refers to the personality of the writer within the text. This does not equate with his or her character in life: in The Canterbury Tales Chaucer assumes the persona of an innocent and credulous pilgrim but he was a sophisticated man. Even inside this work he shows himself, as narrator, to be shrewd and critical.

Free verse and blank verse

These terms are often misunderstood:
Free verse has no set rules such as specified length of line or rhyme. The poet and reader must pay attention to such aspects as natural rhythm, effectiveness of having some short and some longer lines and use of unregulated length of stanzas.
Blank verse has no rhyme but does have a formalised line length of five iambs and is therefore in unrhymed iambic pentameters. An iamb is a two-syllable unit with the weak stress first and the heavy stress second as in the word again. A line of blank verse follows the rhythm of five repetitions of this word: again, again, again, again, again. Much of Shakespeare's verse is written in iambic pentameters as are true sonnets.
Sometimes, particularly at the beginning of a line, the first foot may be inverted with the stress on the first syllable. A foot is the name given to each unit when the line is analysed and so an iamb is an example of a foot.

Grammatical mood

This term refers to verbs and the mood of the speaker/writer. Fortunately in English, it is a simple matter and one we do not have to worry about.
The imperative mood is that of commands: Go away!
The indicative mood is the normal one when we tell of what will happen, has happened or is happening: I shall go; I went; I am going. Note that it applies to any tense of the verb.
The subjunctive mood hardly exists in English but, if you learn French, you will have to master it as the mood of uncertainty and emotional input.

Separate and desperate

The spellings of these two words often cause confusion. Perhaps it helps to recall the root of the latter: "spero" meaning "I hope".