simply/just/only

i simply love it 就
i only love it 只
i just love it 就
i just cant understand 就
i simply cant understand 就
i only cant understand 不能这样说
基本上simply可以和just互换only通常用作【只】
it only happens when...（条件）
it just happens (没办法)
it simply happens 不这样说
it just happened once
it only happened once
it simply happened once
这时全同义
just do it 做【就】是了
im just fine 语气,强调,有【反正】的意思
其实just用法太多了,要深究得花时间滴

既然simply 在字典中的同意词有just, only, 那么他们在词意上,用法上的区别是微小的. 很难区别.
那么既然没区别,或者说区别很小,为什么还多了个词出来? 这就要从词源来找答案了. 字典里给出了下面的注释:
(simply) simple : Middle English: from Old French, from Latin simplus.
just ...