What’s the difference between congenial and genial? They both derive from that Latin term that also developed into genius, but their meanings are mostly distinct.
Genial means “friendly” or “sympathetic,” or “mild”; it also describes someone who displays or is marked by genius, but that is a rare usage. Genial can refer to a person (“She has a genial personality”) or to an inanimate object or phenomenon (“The weather was genial yesterday”).
Although congenial can be synonymous with genial, the connotation is usually one of having a pleasant and/or sociable attitude (“He is a congenial host”) or being harmonious or of a kindred spirit (“Their congenial interest in the matter may help them cooperate”).
Writers must take care not to introduce an extraneous letter to produce one of two words that, though distantly related to genial and congenial, have nothing to do with the terms — or with each other: Genital refers to the sexual organs, and congenital usually refers to diseases or unhealthy psychological features.
A congenital physical condition is one that dates or exists from birth or is acquired during gestation and not through heredity; one can also describe someone as having a congenital fear of or obsession about something. People are also sometimes described as being congenital in some aspect of their nature — for example, a congenital liar is someone who is habitually deceitful.