There's actually a LOT of ways to express "think" in Chinese. There's also '看“, like in this sentence: 你看怎么样？(what do you think?) and 感觉(which is much like 觉得) 以为　means to "mistakenly think" something.　The same way in English when you say you *thought* something, it implies that what you were thinking is in fact not true. 我以为他没有女朋友－I thought he didn't have a girlfriend. [but he actually does] 想 has a few meanings; to think, to want/would like to. It is like the desire of wanting to do something, but not necessarily meaning the action will happen: 我想出去外面，可是没什么打算。－I would like to go outside, but I don't have any plans. It also means 'to think', 他有姐姐吗？－Does he have an older sister? 我想没有－I don't think so. 我在想办法－　I'm thinking of a method. 我想你 - I miss you. 想 is the most flexible out of all of them because it has so many meanings. 觉得 means "to think/feel." 我觉得她很可爱－　I think she is so cute[this is my opinion] 我觉得不舒服－ I don't feel well. 认为 is more like "believe" as in "我认为很多人住美国，可是我没去过，这就是我的想像。(I believe many people live in America, but I haven't been there. This is just my thinking.)

想 = pensar 觉得=achar 认为=considerar

Maybe I've got this wrong, sorry if I do. But I was told there is a big difference between 认为 and 以为。认为 is "think" or "believe" but 以为 means you thought something, but you were wrong. For example, 我以为你是美国人 would mean "I thought you were an American," with the implied meaning that the person actually is not American -- you just had the wrong impression. A: 我是加拿大人。(I'm a Canadian.) B: 真的吗？我以为你是美国人。(Really? I thought you were American.) A: 不是，我住在多伦多。(No, I live in Toronto.)

觉得，to think. 我觉得这家餐厅的菜很好吃，你觉得呢？ 认为，to believe. 我认为沟通很重要。 以为, which is more like be supposed or, I though it should be ..., but........原以为他不喜欢我呢，结果他喜欢我。 想 1, to think. 我想你是对的。 2 to miss. 我想家人了。 3 to want. 我想吃中餐。 如果不清楚，可以问我。

认为and觉得have the same mean.想has two mean.like "want"and"think"For example:我想吃饭=I want have meals.我想你是对的=I think you are right.以为means you had a idea,but it is opposite to the fact.For example:我以为你是对的=i imagined you r right.(in fact u r wrong)