The informal and casual nights are now all 'smart casual and above' and jackets are not necessary. Some men wore them, some didn't. My husband wore chinos and short sleeve shirts some nights and a linen suit others.

Probably not - I'ts informal although I like to wear a different jacket every night unless it's really too hot. I mean you are on a cruise so you don't want to see yobs in tee shirts and 3/4 shorts in the restaurants. Bear in mind the last cruise I was on the restaurant staff were impeccably dressed in their pale green jackets

As the man says but there is no need to wear a jacket however I believe that a well dressed man is preferable to one who isn't. (I was going to say an undressed man but that may not be true). .... Ida

There is no such thing as Informal nights on Celebrity any more - just formal and 'smart casual and above'.