I know the question regarding the difference has been asked but the answers didn't really help me in the other post. I'm trying to recall what my Chinese teacher once taught me.
理解 is when you can understand why something/someone is how it is, but 了解 is more of a deeper connection or understanding of someone.
For example: If you went to an area with a lot of poverty and lived there for a bit, could you say that you finally 了解 them? Sorry for the mix of Chinese and English haha.
Is this correct?
理解: (v) to understand; to comprehend
了解/瞭解: (v)to understand
For example: 理解到人際關係是基於互相利用的原則 "comprehend (the concept of) interpersonal relationship is based upon mutual benefit of self-interest."
For example: 了解他的心情 (clearly)understand his feeling.
Chinese verbs are usually made up according to this formula: modificator + modificated or modificator + a verb to modify. So when I seen that 理解 and 了解 ending with the same charecter (解), this usually means that there is a slight modification of a verb 解(to divide) is in play.
So let's find the roots of the word:
理 (11) リ As per 里# (long strip) + 玉 jewel → veins or streaks in a piece of jade → logic; reason (← lines/threads of a reasoning process ← vein; streak) → principle; natural science.
So here we already see the connotation which 理 brings: lines/patterns of reasoning. Now add this to 解 and you have "to understand解(split/crack) by reasoning理".
Now about 了 which is 瞭 simplified:
瞭 (17) リョウ As per 尞# as described in 僚 (circular continuum) + 目 eye → observe from a high place, enjoying a clear panoramic view → *clear-sighted; clarity.
Now you add everything up and you have: "to understand 解 clearly or by observation (not by reasoning理)"
理解 seems to imply empathy. Examples: 希望你能理解。I hope you would understand. 我可以理解的。I can understand why. 令人难于理解。It is hard to understand why.
了解 seems to mean "To find out or To have realized the situation". Examples:
我想了解具体情况。I would like to know the specifics of the situation. 我了解你的意思。I know what you mean.
理解 is more of a process while 了解 is more of a state. For example, 你能理解吗/难以理解/你能理解我的意思吗，all of them imply the process to complete something;我想了解一下情况/我对中国不是很了解，all these instances imply the extent of understanding or konwing. However when used as noun, the difference is more obvious, 理解 denotes inner thought of your mind, and 了解 means you know some facts of outer world.
In my opinion, 理解=understand，了解=know
