mutable
MYOO-tuh-buladjMeaning able or likely to change
Memory hook MUT = MUTATE: able to change. The octopus turns red, then blue, then sandy brown to match whatever it touches. A creature that changes that easily is mutable.
Spring weather is mutable: sunshine at noon, hail by three.
In context The rules of the backyard game proved mutable; each new player who joined suggested a change, and soon nobody remembered how it had started.
Similar changeable, variable, alterable, fluid
Opposite immutable, fixed, constant
From Latin mutabilis, from mutare, “to change.”