1 [U] the physical or mental strength or energy that you need to do sth; sth that takes a lot of energy 体力；脑力；精力；努力: They have put a lot of effort into their studies this year. 今年他们在学习上倾注了不少心血。He made no effort to contact his parents. 他没有尝试跟他父母联系。

2 [C] an effort (to do sth) something that is done with difficulty or that takes a lot of energy 难办的或费力的事: It was a real effort to stay awake in the lecture. 要在那堂课上不打瞌睡，真得费很大的劲。