"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).

humanitarian

hostile takeover

experimental study

palliative care

ichthyological

accidentally (unexpectedly, unintentionally)

secondary

Kyūjitai form of 初歩的

(chiefly Internet slang) thinking with common sense