not understand; not know how, not know; not be able to tell
→ が
phraseUncommon#11,803
not understand; not know howUsed when you cannot understand or figure out something, such as its meaning, rules, or method. The が phrase names what you do not understand.
JA: かくれんぼのルールが分からない。
EN: I don’t understand the rules of hide-and-seek.