- a cardinal number, 40 plus 5.
- a symbol for this number, as 45 or XLV.
- a set of this many persons or things.
- amounting to 45 in number.
- a gramophone record played at 45 revolutions per minute
- a pistol having .45 calibre
- the Forty-Five British history another name for Jacobite Rebellion (def. 2)
