Demeanor means the outward manifestation of personality or attitude," demeanor suggests one's attitude toward others as expressed in outward behavior. For example : The professor's friendly and laid-back demeanor made him a favorite among the students. While behavior means the manner of behaving or conducting oneself . For example : Her behaviour is often appalling. Synonyms of demeanor include attitude, manner, bearing Synonyms of behavior include actions , conduct In a summary, behavior is the way someone behaves while demeanor is the way someone looks and behaves, which shows you something about their character or feelings.