Dictionary

To authenticate by means of belief; to surmise; to suppose to be true, especially without proof

Example: We assume that, as her parents were dentists, she knows quite a bit about dentistry.

To take on a position, duty or form

Example: Mr. Jones will assume the position of a lifeguard until a proper replacement is found.

To adopt a feigned quality or manner; to claim without right; to arrogate

Example: He assumed an air of indifference

To receive, adopt (a person)

An assumption.

Haughty; arrogant