**Definition of 'think through' : to think about all the different parts or effects of (something) for a period of time especially in an effort to understand or make a decision about it "I need time to think this through." "We have thought through the matter and have come to a decision." **Definition of 'think over' : to think about (something) for a period of time especially in an effort to understand or make a decision about it "I'll give you time to think my offer over." "I've thought over what you said, and you're right." **Definition of 'think of' :to consider doing something "I’m thinking of moving to Sydney." **Definition of 'think about' :to remember someone or something "I was just thinking about you when you called." ****I would say that 'think over' and 'think through' are pretty interchangeable given their definitions but 'Think through' is kind of like analyzing a situation and trying to understand all the different aspects before deciding. 'Think over' is usually more when you already know all the facts about an issue and you're just trying to come to a decision. ****What is the difference between 'Think Of' and 'Think About'? 'Think of' is used to express remembrance. In other words, you can say that think of is used when you call something to mind. The expression 'think about', on the other hand, expresses the sense of ‘interest due to affection or any other feeling.’ The expression 'think of' is more momentary than 'think about' in terms of duration of thought. In other words, the expression 'think about' suggests that the thought is a lengthy one whereas the expression 'think of' suggests that the thought is a short one.