Important, perhaps, as an organizing-and-understanding principle when dealing with people: the "Big Five personality traits". Statistical analysis finds five dominant dimensions of mind: Openness, Conscientiousness, Extraversion, Agreeableness, and Neuroticism. (A handy initial-letter mnemonic is OCEAN.) Descriptions, condensed from Wikipedia:

• Openness — inventive/curious vs. consistent/cautious — artistic, adventurous, creative, imaginative, independent — seeking novelty and variety — as opposed to persistent, pragmatic, dogmatic, closed-minded
• Conscientiousness — efficient/organized vs. easy-going/careless — dependable, self-disciplined, dutiful, planning — perhaps stubborn or obsessive — as opposed to flexible, spontaneous, sloppy, unreliable
• Extraversion — outgoing/energetic vs. solitary/reserved — energetic, positive, assertive, sociable, talkative — perhaps attention-seeking and domineering — as opposed to reflective, aloof, self-absorbed, shy
• Agreeableness — friendly/compassionate vs. challenging/detached — cooperative, trusting, helpful, well-tempered — perhaps naïve, submissive — as opposed to competitive, argumentative, untrustworthy
• Neuroticism — sensitive/nervous vs. secure/confident — vulnerable to stress, anger, anxiety, depression, loss of control, instability — as opposed to calm, stable, maybe uninspiring or unconcerned

^z - 2018-03-26