For us, “想” literally means “think”. However, - Cchatty

For us, “想” literally means “think”. However, “要” means “want”. For example, “我想你” means “I miss you”, or “I am thinking about you”, whereas “我要你” means “I want you”. So, their basic meanings vary a lot.

Then, why do they both mean “want” in textbooks and dictionaries? When we say “我想買一杯咖啡”, in our brain the logic is “I am thinking about buying a cup of coffee.” Instead, “我要一杯咖啡” is literally “I want a cup of coffee”. Thus, they reach the same meaning “I want a cup of coffee” through different logic. Following this difference, “我想要一杯咖啡”, “ I am thinking that I want a cup of coffee”, 我想要買一杯咖啡, “I am thinking that I want to buy a cup of coffee”.

How to use these two well? Normally, we will add a verb after “想” to express the meaning “I want to do something”, “我想游泳” “I want to swim”, “我想買東西”,” I want to buy things”. To compare, “要” could add both nouns or verbs, “我要游泳”, “I want to swim” or “我要一杯咖啡” “I want a cup of coffee”.

the tones among these two usages differ a little bit. “想” normally is softer, more indirect, and sometimes more polite. “要” is much more direct, sometimes rude. Also, when we use “要”, like “我要游泳”, that sounds like you have already decided that you are going to swim, but “我想游泳” is more neutral, it could either be a plan that you have already settled, like “我要游泳”, or it is only a desire, and whether you will do that or not is clear.