When we use the word sentence we usually mean a complete grammatical unit which makes sense in itself and is followed by a full stop. It contains a main finite verb, one with a subject and tense, and may have additional clauses tacked on.
The original derivation was the Latin sententia indicating feeling, from which we also have sense, sentiment etc. The term subsequently broadened to denote opinion or judgement which was the starting point for our modern usage in the courtroom. The judge delivers his verdict and orders that a sentence be applied. It is ironic that this context is supposed to be free from the clouding effects of emotion, previously denoted by the word. As so often, the adjective has taken a different turn and sententious (full of meaning) has come to be pejorative, indicating pompous moralising.
Chaucer had fun with the concept: the rooster, Chanticleer, in "The Nun's Priest's Tale" quotes lofty Latin sententiae as part of the mock-heroic trope and the Wife of Bath, in her Preamble, twists recognised sayings to fit her purpose. The spurious Pardoner refers to Radix malorum est cupiditas (greed is the root of all evil) whilst lining his own pockets with pressured offerings from the poor. Chaucer was well aware of such elements of Ciceronian rhetoric and a knowledge of some of them is essential to a full understanding of his work.
