Being smart is strategic and professionalism loses impact without professional-looking clothing to match...
Make sure your dress fits in. If everyone else comes to work in jeans, then don't insist on wearing a suit.
If the office policy is to wear suits, then you must do so.
Check what colleagues wear and take the lead from everyone else to see if ties are de rigeur.
Think about the day ahead: meetings with clients may require some more thought than a quiet Friday.
Inappropriate dressing is very counterproductive. Girls who wear very short skirts, sheer fabrics or low-cut or cropped tops may find that their professionalism is called into question and they may not be taken seriously in the workplace.
If in doubt about the propriety of a certain garment, then remember that if you have to think about it, then it's probably not appropriate.
Dress Down Days
Policy can vary from company to company, but wherever you work, be assured that dress-down policy does not mean that 'anything goes'.
'Smart casual' is an often-used expression. This usually means smart denim; no sportswear; nothing that might be construed as beachwear, such as shorts.
If you feel more comfortable wearing a suit, then you could do so. But remember that refusing to join in and conform to a dress-down policy may be construed negatively by an employer or by fellow colleagues.