"Historical kana usage", a prescriptive method of using kana to write Japanese. Devised in the Edo period by Keichū (契沖) and taught in schools until 1946, it aims to be etymologically faithful and reflects earlier stages of the language (Heian period and earlier).

as far as ... is concerned; in terms of ...

a target, a mark, a bullseye / an objective, an object (of doing something)

(colloquial) current boyfriend

everything

(slang) Alternative form of 彼氏 (kareshi, “boyfriend”)

everyone, one and all

research & development; R&D

(education) research project, done by Japanese schoolchildren during summer break, to be presented upon return to school

a research student (i.e. a visiting or non-matriculating graduate student) / a researcher