jacklong  +  95986 Wed, 04 May 05 08:21 AM Although I have seen several posts here about the differences between 'which' and 'that', I am still a little confused. I came across this sentense today, and I was not sure about why 'that ' is used here, because 'which' seems also be correct to me. So please help me analyse the structure of this sentense and decide whether 'which' is replaceable here: "A microscope is an instrument that magnifies extremely small objects so that they can be seen easily." Thank you in advance. jacklong Joined on Fri, Oct 29 2004 China Full Member 105 high profile manner a low-key man. Tenses

	Mister Micawber  +  96008 Wed, 04 May 05 09:25 AM 'Which' can generally replace 'that' in restrictive clauses (and would probably be better in your example, in order to avoid repeated 'that'). The main exception is that 'which' cannot replace 'who', while 'that' can. In non-restrictive clauses, use 'which' only. Mister Micawber Joined on Wed, Aug 4 2004 Yokohama Veteran Member 30,788 'The question is,' said Humpty Dumpty, 'which is to be master-- that's all.' Clauses

	jacklong  +  96044 Wed, 04 May 05 10:46 AM First of all, thank you so much, Mister Micawber, but could you please further explain me what restrictive clause is and it would be much better if you could give some examples. Thank you again. jacklong Clauses

	paco2004  +  96051 Wed, 04 May 05 11:13 AM One thing I could add to MrM's answer is that 'that' cannot stands as an object of a preposition. (o) This is the house which Captain Cook lived in two centuries ago. (o) This is the house in which Captain Cook lived two centuries ago. (o) This is the house that Captain Cook lived in two centuries ago. (x) This is the house in that Captain Cook lived two centuries ago. As for restrictive and non/restrictive clauses, you can take the following as the examples; [restrictive relative clause] (o) He has two books which are written in English. (o) He has two books that are written in English. = He has two books written in English. He might have more than two books, but two of them are written in English. [non-restrictive relative clause] (x) He has two books, that are written in English. (o) He has two books, which are written in English. = He has two books, and they are written in English. He has only two books, and all of them are written in English. paco paco2004 Joined on Wed, Nov 17 2004 Senior Member 4,095 In Japan today even dogs are learning how to bow-wow in English. Prepositions, Clauses

	Mister Micawber  +  96088 Wed, 04 May 05 02:07 PM Thanks, Paco. Jack, a restrictive clause adds critical definition to its referent, and a non-restrictive clause merely adds extra information. There is more explanation HERE Mister Micawber Clauses, Commas