1. (adjective) able to exist under more than one set of conditions

• biological science
• biology

1. (adjective) granting a privilege or permission or power to do or not do something

• enabling

2. (adjective) not compulsory

• optional

1. (adjective) of or relating to the mental faculties

• faculty
• mental faculty
• module

1. (adjective) able to exist under more than one set of conditions

• obligate