From Traderpedia

Definition: Total earnings less expenses.

Profit is the difference between the selling price (S) and the purchase price (P), less commissions (c), spread (s), and carrying (interest) charges (i).

<math>(S-P)-(c+s+i)</math>

In the case of a short sell, profit is the negative of the difference between the Purchase price and the selling price, less commissions, spread, and carrying (interest) charges.

<math>-(P-S)-(c+s+i)</math>