Then what is that definition?
But aikido is not abstract. An aikido technique, when performed correctly, produces a specific, measurable, physical result. What place has abstraction in there?
It is sometimes useful to reference them all at once. The reason that logic doesn't extend to ki is that the word ki doesn't explain itself. The Greek roots of biomechanics make it abundantly clear to anyone who speaks a language that makes a lot of use of Greek (like English and most Slavic and Romance languages). I can simply say the word and everyone knows what I'm talking about and, just as importantly, what I'm not talking about. Not so with ki.
Specificity and clarity are not clutter. The subtle differences between synonyms allow us to convey nuance.
The problem with ki isn't that it is a word for something else. The problem with ki is that, when used, it makes things less clear; it is a stumbling block to communication rather than an aid to it. (Note here that I am referring specifically to ki as we use it in the martial arts, not the many ways it is used in the Japanese language.)
You are saying that you'd rather not use the term ki
, because its meaning is not clear enough to be helpful for learning how to use your body.
That may be true, but why do you expect explanations from physics to be more helpful? Explaining about gravity, friction and mechanics in general will not help me much either when I want to learn to ride a bike, become a ballet dance or a martial artist.