The definition of a sentence in general is that it makes complete sense. But some sentences, as in from a fictional book, e.g., 'Of course he is rich, but the rich were usually mean.' , these do not seem to make any complete sense to me as an ESL student. They require context for complete understanding? I mean to me this just sounds like a jumble of words all pasted together, more like two phrases at best but it is presented as a sentence.
I am confused, can somebody please clear up if this is a sentence or not and if so why and why not, much grateful in advance.
lumensluminiscenceThe definition of a sentence in general is that it makes complete sense.
That's complete nonsense that is told to beginners. It is soon passed over and forgotten in preference to matters like subjects and predicates, which are the true components of sentences.
What you have here is a compound sentence.
Of course [he]subject [is rich]predicate, || but [the rich]subject [were usually mean]predicate.
CJ
A useful definition of a sentence is "one that contains a main clause or a coordination of main clauses".
Your example consists of a coordination of two main clauses:
of course he is rich + but the rich were usually mean.
Note that each coordinate contains a subject and a finite verb.
I think you are remembering that wrong. A sentence expresses a complete thought, not complete sense. That is a broad definition. My definition is even broader: a sentence is a word or series of words that starts with a capital letter and ends with the appropriate mark of punctuation. But your English teacher hopes you will first learn to construct sentences that conform to a narrower definition, and that will serve you well when you go on to be more creative: a sentence is built around at least one independent clause.