I assume you mean in the role of relative pronouns, and that you are talking about things, not people or places. Short answer: you can always use "which", but you can sometimes substitute "that". "Which" can always be used in that role, whether as in "identifying" or "restrictive" relative clause, that is one that limits the noun it refers to what is described in the relative clause, or as a "supplementary" relative pronoun, which describes the noun without actually limiting. The second is distinguished by a comma that sets it off (as in the last sentence). Additionally, "that" can be used instead of which, but only as a restrictive relative pronoun, and only if it directly follows the noun that it describes (as I just used it). Some examples: - "The letter which/that I wrote" (object pronoun, restrictive) - "The letter which/that is in the mail" (subject pronoun, restrictive) - "The opera Don Giovanni, which I love" (object pronoun, supplementary) - "The job for which I applied" (object pronoun used with a preposition, restrictive) Additionally, "that" can also be used in a similar fashion as an alternative to "who" or "whom" in connection with people (although some people disapprove of this usage), whereas "which" really can't (although you may see some examples in older texts).

Which one do you want? That one. "That which does not kill us makes us stronger." - Friedrich Nietzsche

Which =which one you want? Thas is my car. Which =cuáles That,= eso, esa

Which is like... "Which store are we going to" That is like "That is the store"

Please , write English.