In class we are learning subject-predicate (ay) and predicate-subject sentences. The professor asked us if this sentence was grammatically correct: Ang mga estudyante si Tom at si Alex. The professor said this sentence was incorrect because it needs ay. I thought this sentence was correct because si Tom at si Alex could be the subject and Ang mga estudyante could be the predicate. This is how I interpret the following sentences (underlining the subject and bold the predicate): [P-S] Ang mga estudyante si Tom at si Alex. Tom and Alex are the students. [S-P] Ang mga estudyante ay si Tom at si Alex. The students are Tom and Alex. So my question is, doesn't ang act as a definitizer in the original sentence and it is grammatically correct in predicate-subject form? My professor said Mga estudyante si Tom at si Alex would be the correct predicate-subject form, but wouldn't that translate to Tom and Alex are students and not Tom and Alex are the students? Or is it that Mga estudyante si Tom at si Alex is ambiguous and can mean both? Second question: Can ang follow ay? Si Tom at si Alex ay ang mga estudyante. Tom and Alex are the students.