think: is general and may apply to any mental activity, but used alone it often suggests the attainment of clear ideas or conclusions: a course that really teaches you to ~.
cogitate: implies a deep or intent thinking: quietly sitting and ~ing. (intent有2个意思 1、专注的showing strong interest and attention，如an intent gaze/look专注的目光/神情，如his eyes were suddenly intent他的目光突然专注起来，如I was so intent on my work that I didn't notice the time我专心工作，以致忘了时间 2、决心做（尤指伤害他人的事）determined to do something, especially something that will harm other people，如they were intent on murder他们存心谋杀，如are you intent upon destroying my reputation你是不是存心要败坏我的名誉？)
reflect: suggests the unhurried consideration of something called or recalled to the mind: ~ed on fifty years of married life.
reason: stresses a consecutive logical thinking: ~ed that the murderer and victim knew each other. reason推理是连续的、逻辑的思考，因此逻辑logical是更基础的词。逻辑指有秩序，清楚，不偏颇(ordered, clear and free from bias)，经常会用到reason和logic，两个词请一起记 注意murderer和victim用一个the限定即可
speculate: implies a reasoning about things that are theoretical and problematic: historians have ~d about the fate of the Lost Colony.
deliberate: suggests a slow or careful reasoning and consideration before forming an opinion or idea or reaching a conclusion or decision: the jury ~d for five hours.
think思考: 泛指任何脑力活动，单独使用表示获得了清晰的想法和结论，cogitate沉思: 强调深沉专注的思考，reflect反思回想: 指慢慢考虑当前想到的或回忆的事情，reason推理: 强调有顺序有逻辑的思考，speculate推测推断投机: 针对理论性的不确定的事物的推理，deliberate深思熟虑: 形成意见做出结论前仔细慎重的思考或推理
记忆方法: 1）思考的意思是构思判断推理等脑力活动mean to use one's powers of conception, judgment, or inference.
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