Is there much difference between a professional businessmen's suits and men's casual suits?

We haven't enjoyed and been entertained by men's casual suits since the 70s.  A sport coat with casual pants is more casual than a traditional tailored suit. 

 

  It depends on many factors, such as the level of formality of the wedding and on your position there. Is it an extremely formal wedding or a casual wedding, and are you part of the wedding party? Will all men be in tuxedos? Are you a guest and not closely related to or closely associated with the bride and groom? Will you be in any of the focused photos or part of the video that focuses on the main players?

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