Cheap, New, Old, Fast

Four い-adjective roots you'll adverb-ify constantly. 安い (yasui, cheap), 新しい (atarashii, new), 古い (furui, old), and 早い (hayai, early/fast) — drop the い for 安く, 早く and you're describing how, not what.

安 is やす.い (cheap/at ease) — アン in 安心 (relief). 新 あたら.しい — シン in 新聞 (newspaper). 古 ふる.い — コ in 中古 (used). 早 はや.い (early) — ソウ in 早朝; shares はやい with 速い (fast in speed).