Semi-Open vs Semi-Closed Files


There are no semi closed files as a separate term. There are only open, half open and closed files.
Open file is a file where both your and the opponent's pawns have been traded off.
Closed file is a file where both pawns are still on the board.
Half (or semi) open file is a file where one pawn is on the board, but the other is not. This file is exploited by the side whose pawn is not on the board.