Adjectives

(a)informalnot formal“conservative people unaccustomed to informal dress”, “an informal free-and-easy manner”, “an informal gathering of friends”
(a)informalused of spoken and written language
(s)informal, loosenot officially recognized or controlled“an informal agreement”, “a loose organization of the local farmers”
(s)cozy, intimate, informalhaving or fostering a warm or friendly and informal atmosphere“had a cozy chat”, “a relaxed informal manner”, “an intimate cocktail lounge”, “the small room was cozy and intimate”