First window may refer to: first broadcast syndication rights for a work the post-grant review period for third-party challenge and opposition of a pending patent or trademark a wavelength band or transmission window in fibre-optic communications the initial 4-6 hour period of ischemic preconditioning, known as classical or early preconditioning, in which a coronary occlusion can limit injuries of a subsequent ischaemia reperfusion in the myocardium See also Second window (disambiguation) Window (disambiguation) Windowing (disambiguation) Windows (disambiguation)