This is the 770th most frequent Chinese word.
解
"解" means "to solve," "to untie," "to explain," or "to understand."
Here, '解' is used as a verb meaning 'to solve', in the context of resolving mathematical problems.
他能解所有复杂的数学问题。
He can solve all complex math problems.
In this instance, '解' is used within the word '理解', which means 'to understand', referring to comprehending someone's suggestion.
我们需要好好理解他的建议。
We need to understand his suggestion well.
In this sentence, '解' functions as part of the verb '解开', which means 'to decipher' or 'to unlock', in the context of solving a password.