Dear
daagh,
My intelligent colleague, these are interesting questions.
I've never heard any grammar definition include anything about "
number of thoughts," because as soon as we get to counting how many thoughts are or aren't in a sentence, we are on extremely slippery ground. What on earth is exactly "one thought"? What that a thought?
The definitions I have heard all revolve around number of S-V pairs--much more concrete.
In my understanding, a simple sentence has a single clause, a single S-V pairing that anchors the sentence. We could have multiple subjects in parallel or multiple verbs in parallel. I have no problem calling this a simple sentence:
The animals snarled and screeched and growled and whinnied and whimpered and hooted and howled and gobbled up the whole ice cream stand.
Technically, if the subject or verb is elided in parallel structure, grammatically it still "counts" as if it is there. I am guessing that this sentence would be understood to have two independent clauses in parallel:
He is a great singer and she, a great dancer.
Similarly, this one would have three independent clauses in parallel:
The teacher walked into the classroom, greeted the students, and took attendance.
I am imagining that, technically, these would be compound sentences. At some point, it's a purely theoretical decision.
I think I would say that in the discussion of sentence structure, the distinction of simple vs. compound is not the most important. The distinctions of simple vs. complex and and compound vs. complex are the ones that really confuse people and really need to be understood.
Those are my thoughts.
Take care, my friend.
Mike