Fashion
Women - A skort and some type of blouse is a professual outfit
Fashion Men - Jeans and a Blazer
Meetings - when meeting your colleagues for dinner after work, you need to maintain a level of 'professualism'. You cannot be too casual because you have to work with them, but you don't have to be professional about everything.
Dialogue - when talking to authority or colleagues about a social event that work is hosting, a phrase such as "What are you gonna wear?" is preferable to "What are you going to wear?" In the context of email between colleagues; signing off with "Take it Easy" v.s. "Best regards" or "Later
man" v.s. "Sincerely" can be considered 'Professual'
Events - Professual
Friday instead of Casual
Friday, because no one actually knows what is acceptable on casual
Friday's but when it is 'Professual
Friday', the individual knows that there has to be an element of professionalism in your outfit.