(electronics) pentode (vacuum tube)

pentathlon

five days in the week

to grumble (about something trivial)

(history, government) the Five Guards under the 大宝令 (Taihōryō, “Taihō Code”) (衛門府 (Emonfu, “Gate Guard”), 左衛士府 (Saejifu, “Left Guardsmen”), 右衛士府 (Uejifu, “Right Guardsmen”), 左兵衛府 (Sahyōefu, “Left Soldier Guard”) and 右兵衛府 (Uhyōefu, “Right Soldier Guard”))

a surname

the five lakes around Mount Fuji: 本(もと)栖(す)湖(こ) (Motosu-ko), 精(しょう)進(じ)湖(こ) (Shōji-ko), 西(さい)湖(こ) (Sai-ko), 河(かわ)口(ぐち)湖(こ) (Kawaguchi-ko) and 山(やま)中(なか)湖(こ) (Yamanaka-ko).

(idiomatic) living a life without achieving anything great

eleven o'clock

twelve o'clock; noon; midnight