used as the subject or object of a verb to show what thing or things you are referring to, or to add information about the thing just mentioned. These sound the same but spelled differently and mean different things - they're homophones. Let's go over the meanings and patterns. Which twin is which? They look exactly alike to me. How can you tell which is which? Which is a question, phrase or pronoun. Which is which? Which one is which? Which is correct? Which one do you want? Knowing how to use which and that correctly is important because these words have different meanings and thus affect sentences’ meanings. If the details are crucial to the sentence, use that. If they aren’t crucial, use which. Which and that are probably words you use frequently. WHICH IS WHICH definition: 1. used in expressions that relate to being able to see the difference between two very similar…. Learn more. The meaning of WHICH is being what one or ones out of a group —used as an interrogative. How to use which in a sentence. One of our experts will correct your English. Both which it is and which is are correct, but they are used in different contexts. Which it is is used when referring to a specific thing or situation, while which is is more commonly used when introducing a clause or providing additional information. On the other hand, “which” is an interrogative pronoun that may pose questions with restricted or fixed answers. It can also be used to insert a clause that provides information unrelated to the main sentence. While ‘that’ can be used as a determiner, pronoun, or adverb, conjunction can only be used as a determiner and pronoun. Whether to use that and which depends on whether the clause it introduces is restrictive or non-restrictive. A restrictive clause means that the information in the clause is necessary to understand the preceding noun. For a restrictive clause, use that. Let’s look at some sample sentences: 'Which are' refers to plural nouns or options, while 'which is' refers to singular nouns or options. This phrase is correct when referring to plural nouns or options. Use 'which are' when you are asking about multiple things or options. Which are your favorite colors? I can't decide which are the best movies to watch. The meaning of WHICH IS WHICH is —used to say that one is unsure about the identity of each member of a group. How to use which is which in a sentence.