SOLAR SYSTEM

Detailed explanation-1: -Intermediate, moderate, semihard or semisoft might work, depending on the context. Although the last two actually contain hard or soft. Hopefully that helps, or gives you a starting place.

Detailed explanation-2: -The pairs “hard/soft” and “hard/easy” define our two most common ways of using the word “hard”. The word “hard” has been part of the English language for a very long time. The same word, with the same spelling (hard), can be found in Old English, although the word could also be spelled heard.