It's difficult to understand his explanation.

This problem is very difficult.

It's difficult to understand the nuance of that word.

It's difficult to understand his explanation.

His words always resonate in my heart.

His kindness is so great that it's unable to put into words.

His kindness is so great that it's unable to put into words.

His explanation was impossible to understand.

Yamato kotoba can be said to be the prototype of Japanese.

He likes to speak using male language.