(grammar) Short for カ行変格活用 (ka-gyō henkaku katsuyō): k-irregular conjugation

difficult / hard, probably impossible

to recall, to remember / to learn / to memorize / to feel (an emotion or sense)

card

(attributive) Alternative spelling of 華氏 (“Fahrenheit”)

Alternative spelling of 華氏度 (“Fahrenheit scale”)

excellent, beautiful, fine, good

The katakana syllable カ (ka). Its equivalent in hiragana is か (ka). It is the sixth syllable in the gojūon order; its position is カ行ア段 (ka-gyō a-dan, “row ka, section a”).

蚊: mosquito

strange, weird, odd