Who, which, that or what: wrong relative pronoun
I understood all what the teacher said.
I understood all that the teacher said.
Who for people, which for things, that for both
Relative pronouns connect a clause to the noun before it. What is not a relative pronoun after a noun or after all, everything or something.
- who / whom
- People. Whom is formal, for objects, often after a preposition. the man who called · the person to whom I spoke
- which
- Things; also after a comma to comment on a whole clause. the book which I read · He passed, which surprised us.
- that
- People or things in defining clauses; always after all, everything, nothing and superlatives. all that the teacher said · the best film that I have seen
What YabLab does with this mistake
- Catches it right as you write — comments, email, docs.
- Explains the why in your language, not just the fix.
- Helps you practice it until it is gone for good.