Formal night is Monday our first day at sea. From what I've observed "formal" has quite a range. Anything from slacks and shirts with ties for men all the way to tuxes. Some women wear ball gowns, some wear suits (I will be wearing a suit), some just wear dresses. Kids usually wear dresses, or little kid formal clothes and some of them wear Disney costumes like princesses and pirates! One of the cutest outfits I saw on kids during our last cruise, were two girls in matching sailor outfits, adorable! And as always you don't have to participate in formal night. It's not required.