My first post. Apologies if this has been asked before; it’s difficult to google.
It seems like they’re not canonical. Jisho and WK seem to differ in some cases.
For example, I am learning the kanji for year (年). Typically I try to spot the radicals beforehand so I can get better at recognizing them. I came up with the life kanji(生) + the drop radical.
WK has the cow radical and gun radical which IMO is not that clear especially since cow already has something gun shaped which looks completely different.
On the other hand, jisho lists the parts as ground, slide, pestle/dry, and second(?). With the main radical being pestle/dry.
It seems that radicals therefore are not strictly defined for each kanji, and maybe they can be somewhat fluid?
For me I think remembering year would be easiest with my interpretation as a mnemonic “a year is a drop of life”. This is the first time I’ve come across this situation though, so I’d like to know what people who actually know kanji think.
Would it be harmful long-term to use my own radical interpretation (within reason) in terms of my ability to understand written japanese?
As of right now I have no plans to learn to write, so stroke order which probably is affected by radical interpretation may not matter.
I think you should remember it in whatever way makes the most sense to you.
Wanikani definitely does not follow the “standard” radical breakdown of kanji, even inventing some of its own radicals, or using non-standard names for radicals to make things easier (see this help section for more info on why) – the Tofugu article linked from that page is also worth a read.
That said, there is always an “accepted” dominant radical for each kanji, which is what you would use to look up a kanji in a kanji dictionary (in the old days, now there are much better methods with various websites and apps). For example, for 年 the main radical (部首) if you look it up in a kanji dictionary (just google “年 部首”) is 干 （かん・いちじゅう）.
However, you will probably never need to know this, and knowing the dominant radical does not necessarily help you remember all the other parts to the kanji, so I think using Wanikani’s or your own is probably best.
As noted, you totally can but you will also have to do your own mnemonics since WK bases them on that.
Personally, I found the radicals helpful up to about level 45 or so. That’s when most of the radicals just start being old Kanji. However, the radicals I learned previously definitely helped long term.
One piece of advice then is to be consistent in the application as much as possible so as not to confuse yourself.
I think the OP question has aready been answered, but I wanna give a shout-out for the Keisei-Semantic-Phonetic script - because WK has a tendency to break down kanji into multiple radicals as you progress. But, those can also be lumped together to form a bigger radical sometimes - which might be easier to remember or construct a mnemonic around.
This script helps you identify on-yomi pronunciation relationships between kanji due to the radials present, so it’s super-helpful for learning those on’yomi - or allowing you to guess them with time!
But, it also helps you see that bigger picture of the radicals used! ^>^