To perceive or apprehend clearly and certainly; to understand; to have full information of; as, to know one's duty.

To be acquainted with; to be no stranger to; to be more or less familiar with the person, character, etc., of; to possess experience of; as, to know an author; to know the rules of an organization.

To perceive directly, have direct cognition of; to have understanding of; to be or feel certain of the truth or accuracy of a fact, etc.

be familiar or acquainted with a person or an object; "She doesn't know this composer"; "Do you know my sister?"; "We know this movie"; "I know him under a different name"; "This flower is known as a Peruvian Lily"

perceive as familiar; "I know this voice!"