Sentence

 A sentence, "a set of words that is complete in itself, typically containing a subject and predicate, conveying a statement, question, exclamation, or compound, or command, and consisting of a main clause and sometimes one or more subordinate clauses." Interesting take.

 Is this considered a sentence? Those five words? This is a sentence! That probably counts. Is the subject unclear? Context says the words themselves are the subjects. 'This' and 'that', and 'considered' and 'sentence'. But, I wrote it, so of course context holds clear to me. To help you, the reader, the subjects are highlighted. Clearer? I should hope so; literature class and all that. Reading comprehension, you know.

 We took a test. Had to write argumentative essays. I learned that I should really make a point to write down my AP classroom password. 

So that's... good to know.