Someone or something adaptable can change in order to do well in a new situation. An adaptable student can learn a new app, a new teacher, a new city. An adaptable tool can be used in more than one way. Plants and animals get the word too, when they can live in more than one kind of place. It is praise, most of the time. The noun is adaptability; the verb is adapt. Though actually, it sits close to flexible, but they are not twins. Flexible often means you can bend this once — a time, a rule, a plan. Adaptable often means you can remake yourself for a new world and keep going. A person can be flexible about a meeting and still not be very adaptable in a new country. You will also hear adaptive in science and tech (adaptive software, adaptive behaviour). For people in ordinary talk, adaptable is the warmer, more common word. It can describe people, plans, rooms, skills. It does not mean “already changed.” It means “able to change if needed.”