In Chinese language, both 想 and 要 can be applied to indicate the intention of plan of somebody. However, there are some differences in tones, which will be explained in the following parts. When the teachers teach Mandarin language, they will tell you that 想is to indicate that someone has the idea or plan to do something but it is not sure that whether it will be implemented or not. Therefore, the tone is relatively weak. If we use 要, we usually express a kind of strong desire or hope, even a kind of decision and resolution. The point is that the speaker will realize it, forming a very resolute tone to realize the hope.

Let’s take two examples to illustrate the application of these two words. In the sentence我想买这台电脑, the speaker just express his idea of buying the computer but it is not sure her will buy it or not finally. However, if you say 我要买这台电脑, you has not only such idea, more importantly, you will put it into the practice. Since the tone of 想is relatively weak, we often use 想when we make a request to the others, making it more polite. For example, you can say老师，我想请你帮个忙.

What’s more, one point that the foreign students who learn Chinese language need to pay attention is that 不or不想is usually used when we express that we have no certain idea of intention. In this case, 不要is not allowed because it is often used to forbid and persuade the others do not do something, being equivalent to 别. A:你要去看演出吗？B：不，我不想去. Teachers need to notice this point because students often regard 不要as the negative form of 不.

In addition, since the tone of 想is relatively weak, we can add some adverbs of degree before it such as 很、非常and 有点儿. For the character 要with strong tone, the words being put before it are usually 一定、非and决 to indicate the resolute tone. We should say我不让他报名，他非要报不可and 我今天有点儿想去看看他.