to know something very well; to be an expert in or deeply familiar with a subject

to be very familiar with; to be conversant with

to know something thoroughly; to be deeply familiar with; to be good at

to not know how to swim; to not be a strong swimmer

to be experienced and have a deep understanding of human affairs or how the world works

to have an understanding of the world or how things work; often used in the negative to describe a young or inexperienced person who lacks worldly wisdom

to know little of how the world works; unworldly and unsophisticated

to be skilled in or well-versed in; to be highly familiar with a subject or skill

to be skilled at; to be proficient in; to be thoroughly familiar with a skill or subject