a free Japanese adjective (自立語 (jiritsugo)) that can be grammaticalized by being attached to an inflectional form of another 用言 (yōgen, “inflected word”)

understanding, comprehension / appreciation

benefit (be or provide a benefit to)

deepen

useless, deadhead, good-for-nothing, a piece of shit / (politics) lame duck

to study / to learn

the Japanese language

understand, comprehend / appreciate

(grammar) an -i adjective: specific to Japanese grammar, an adjective with an attributive form that ends in い (-i) / (grammar) (more generally, such as in another language) an adjective

help, aid / assistance