Adoption is the act of taking something on as your own. Adoption usually refers to the legal process of becoming a non-biological parent, but it also refers to the act of embracing ideas, habits, or free kittens.
Adoption comes from the Old French word adoptare, meaning "to chose for oneself.” Feel like adding an option? Try adoption. Adoption is the noun form of adopt, so it not only refers to legally taking another person into your family, it can be any time you take something on as your own. If you start dressing like a friend, that's an adoption of your friend's style. If that friend wears micro-miniskirts, your parents might put you up for adoption.