1. a person or entity that perceives, knows, or becomes aware of something
Usage: formal or philosophical; less common than 'cognizer' in everyday speech

Examples

• In philosophy, the cognizer is the subject who experiences knowledge.
• The cognizer must have some awareness of the object being perceived.
• As a cognizer of the facts, she was called to testify in court.
• The relationship between the cognizer and the cognized is central to epistemology.