TLDR: I hate 合 (definitions: suit/fit/join).
I made a tier list of the words I have unlocked so far containing 合 along with commentary. Read along if you are interested, or don’t
A tier:
合う = to suit: beautiful. self-explanatory. unproblematic queen
合わせる = to join together: no qualms about this one either, it’s in a similar vein to 合う in my mind
B tier:
知り合い = acquaintance: I don’t really mind this one. If it’s a person you know, and you joined up with them at least once, I can call them an acquaintance.
間に合う = to be in time for: I get this one, like, you were able to join (合) someone/something in the interval (間に) that you planned for. IMO not the best but I’m fine with it.
C tier:
待合 = waiting room: The mnemonic given for this is “The place you wait to join other people is a waiting room or a meeting place.” I mean… I guess so? Though I feel like something like 待室 (wait + room) would make more sense for “waiting room” compared to “wait + join”.
試合 = game: “Attempt + join = game”. Honestly this kinda makes sense to me, in the way that whenever I try to organize game nights with my friends it often ends up being a futile attempt to join together with them. Planning hangouts as adults is hard!!
D tier:
場合 = case: The mnemonic for this one is “What location suits a situation the best? That always depends on the case or circumstance.” I don’t like this one, I mean, “location + suit = case”? Fortunately the mnemonic is simple enough to remember that I answer it right most of the time.
具合 = condition: This one puts a bad taste in my mouth. The mnemonic isn’t the worst: “You have to find the right tool to suit your condition or state.” Okay, fine. But I still get this word wrong all the time because it’s just kinda vague. Do you know the part in the third harry potter movie where that one kid was talking about Sirius Black all ominously, and he’s like “Black could be anywhere… it’s trying to catch smoke with your bare hands”? That’s a visual representation of my brain trying to remember what the heck this word means.
合図 = signal: “Suit + diagram = signal” doesn’t really make sense. Like I guess a diagram that suits the situation can act as a signal? But it’s kinda a stretch. And WK’s mnemonic doesn’t help either: “A diagram everyone joins together to see is a signal or a sign.” Huh? No it’s not? I can look at a diagram all on my lonesome and it still may or may not be a signal/sign. But whatever.
F tier:
合格する = to pass a test: Absolutely not. “Suit + status = to pass a test”? Clearly whoever invented this word didn’t pass their tests in school because this doesn’t make sense at all sorry.
都合 = one’s convenience: I get this one wrong every time. I seriously hate it. Wanikani’s mnemonic even starts off with “This one makes no sense (sorry!).” Like excuse me?! Isn’t it WK’s whole job to come up with good mnemonics that will make me remember the words? But I can’t fully blame WK either because “metropolis + suit = one’s convenience” is simply outrageous
That’s the end of my ramble about 合, hopefully having written this post will make me remember these words better in the future? though probably not tbh