na-adjective
healthy; in good health; robust
Describes a person's physical condition, often used for older people who are still vigorous. Common in greetings and well-wishes.
おじいさんは九十歳でも達者だ。
Grandpa is still healthy even at ninety.
どうぞお達
Please take care of yourself (stay well).
na-adjective
Refers to being good at something, often a practical skill or art. Slightly old-fashioned; 上手 or 得意 are more common in modern casual speech.
彼は口が達者だ。
He is a smooth talker (literally, skilled with his mouth).
祖母は編み物が達者だった。
My grandmother was skilled at knitting.
noun
Noun usage for a highly skilled person. Often replaced by 達人 in modern Japanese, but 達者 can still appear in set phrases or older texts.
See also: 達人
彼は剣術の達者として知られていた。
He was known as a master of swordsmanship.