1. Assess and evaluate usually mean the same thing. The meaning is to consider something and decide what good points and bad points the thing has. Examples: We assessed/evaluated all the persons whom we interviewed for the job opening, and we decided that Sally Jones was the best candidate. 2. Reckon has several meanings. Beware: in America, if you say "reckon," you will sound like you are 来自农村。 Reckon, in 来自农村 speech, means "think." Example: I reckon it's gonna (going to) rain today. Reckon can also mean to estimate. 3. Estimate means to make a rough calculation or educated guess as to the right answer, as opposed to calculating an exact answer. Example: Police estimated that there were 10,000 protesters in the crowd outside the White House.

John 说的对。我再补充几句。首先看得出你英语的热情，不过背字典绝对不是好方法。不要那么学习。而且拿出一些近义词来比较其实也不是好方法，最后你这几个词反而混淆了，没有一定的词汇量和对单词的真正领悟之前，没必要做这些无用功。 Back to your question, 这几个词除了reckon，其它三个还有一点可比性，assess 和 evalute 多用于评价，测评，比如员工表现测评，产品评测，来看看评测对象有多好，多有效之类的。estimate 对我来讲纯粹就是估计之意，估计一下你能跑多远，跳多高之类的。不过不要underestimate yourself, 你在英语方面很有天赋，不然做一个测试，来 assess or evaluate your current English level.