being
Synonym discussion
Sense: noun/1
For noun sense 1, being is the broadest of these words. It can mean a person, an animal, or even something imagined, such as an alien or spirit. Creature usually sounds more physical and often points to an animal or a living thing with a body. Entity is more formal and often appears in legal, business, or philosophical writing when the speaker wants a neutral label. Life form strongly suggests biology or science fiction, so it fits best when life itself is the focus. You can say every human being deserves respect, a strange creature ran across the road, a business entity filed the papers, or scientists searched for life forms on Mars.
Etymology
Being was formed inside English from the verb be. In Middle English, the -ing form of be developed into a noun meaning the fact of existing, and from there it also came to mean a person, creature, or other thing that exists.