flex + -ible

source: Flexible | Anime Amino

capable of bending easily without breaking:

〈物が〉曲げやすい, しなやかな(↔ rigid); 〈人(の体)が〉柔らかい

e.g. flexible rubber seals.

able to be easily modified to respond to altered circumstances or conditions:

〈人･計画などが〉 «…において/…について» 柔軟な, 適応性に富んだ, 融通の利く(adaptable) «in/about» (↔ inflexible); 〈子供などが〉言うことをきく

e.g. flexible forms of retirement.

(of a person) ready and able to change so as to adapt to different circumstances:

e.g. you can save money if you're flexible about where your room is located.

late Middle English: from Old French, or from Latin flexibilis, from flectere ‘to bend’.