Castle vs. Fortress

Difference Between Castle and Fortress
Castlenoun
A large building that is fortified and contains many defences; in previous ages often inhabited by a nobleman or king.
Fortressnoun
A fortified place; a large and permanent fortification, sometimes including a town; for example a fort, a castle; a stronghold; a place of defense or security.
Castlenoun
(chess) An instance of castling.
Fortressnoun
(chess) A position that, if obtained by the weaker side, will prevent penetration by the opposing side, generally achieving a draw.
Castlenoun
A rook; a chess piece shaped like a castle tower.
Fortressverb
(transitive) To furnish with a fortress or with fortresses; to guard, to fortify.
Castlenoun
(shogi) A defense structure in Japanese chess in which the king (玉) is positioned in a certain way so that it is protected by pawns (歩) and silver general(s) (銀) and/or gold general(s) (金) often with an additional knight (桂) and lance (香車).
Fortressnoun
a fortified defensive structure
Castlenoun
(obsolete) A close helmet.
Castlenoun
(dated) Any strong, imposing, and stately mansion.
Castlenoun
(dated) A small tower, as on a ship, or an elephant's back.
Castleverb
(transitive) To house or keep in a castle.
Castleverb
To protect or separate in a similar way.
Castleverb
(obsolete) To make into a castle: to build in the form of a castle or add (real or imitation) battlements to an existing building.
Castleverb
To move the king 2 squares right or left and, in the same turn, the nearest rook to the far side of the king. The move now has special rules: the king cannot be in, go through, or end in check; the squares between the king and rook must be vacant; and neither piece may have been moved before castling.
Castleverb
To create a similar defensive position in Japanese chess through several moves.
Castleverb
(cricket) To bowl a batsman with a full-length ball or yorker such that the stumps are knocked over.
Castlenoun
a large and stately mansion
Castlenoun
a large building formerly occupied by a ruler and fortified against attack
Castlenoun
(chess) the piece that can move any number of unoccupied squares in a direction parallel to the sides of the chessboard
Castlenoun
interchanging the positions of the king and a rook
Castleverb
move the king two squares toward a rook and in the same move the rook to the square next past the king