这个三个词都有：推测，假定之意，但是，含义和用法却大不相同。
1.assume v. 设想，假定，以为，推定
指想当然地将未经证实的事进行设想、假定或推测，比较武断。如：
I didn't see your cell phone, so I assumed you'd left.
我没看见你的手机，所以我以为你离开了。
People assume they know me through and through the moment we meet.
人们一见到我，就自以为对我了如指掌了。
Putting two and two together, I assume that this was the car he used.
根据我的了解，我猜想这是他曾开过的车子。
If the package is wrapped well, we assume the contents are also wonderful
如果包装精美，我们就会认为里面装的也是好东西。
I hope to go to college next year, always assuming I pass my exams.
我希望明年上大学，当然是在我通过考试的前提下。
Assuming that Dad agrees, when do you want to shop for a new car?
假设爸爸同意，你打算什么时候买新汽车？
Assume A knows B is guilty.
假定甲知道乙应负罪责。
Assuming he's still alive, how old would he be now?
假定他还活着，现在有多大年纪了？
I naively assumed that I would be paid for the work.
我天真地以为这活儿是有报酬的。
He assumed, wrongly, that she did not care.
他误以为她并不在乎。
It would be rash to assume that everyone will agree with you on this.
你要是认为在这件事上谁都会同意你的看法，那就太欠考虑了。
I had assumed him to be a Belgian.
我本以为他是比利时人。
I assume that you have heard the news. 料想你已经听到了那个消息。
I assumed that you had known the result.
我假定你已经知道了结果。(虽然我没证据，但我后续所有的行为都基于此假定)
I assume they will wait for us.
我假定她们会等我们。(我不知道真的会不会，但我以她们会等作为前提)
2.presume v. [正式]假设，假定；相信；料想，认为
常指以已有的经验、信息等为依据进行合乎逻辑的推测、推断，有信心有证据的基础上的假定；但结论可能有误。如：
I presumed (that) he understood the rules.
我相信他明白这些规则。
I presumed him to be her husband.
我料想那就是她丈夫。
This logical analysis presumes the separation of subject from object.
该逻辑分析假定主体与客体是分开的。
I presume that this price includes all transportation and accomodation fees.
我猜测，这个价钱包括一切交通费用和住宿费。
I presume you're here on business.
我想你是来这里出差的。
