Something or someone that is mutable is subject to change. Mutable weather can go from sunny, to rainy and windy, and back to sunny again.
The word mutable originally had a negative connotation, and it referred to a person, usually a poet, who frequently changed his mind and moods. Mutable has come to mean anything that is capable of changing form or quality. If your favorite restaurant offers seasonal food, the menu is probably mutable with the change in seasons. In science, the word mutable refers to an organism or a gene that, for better or worse, changes its form.
