Threshold - The beginning of that portion of the runway usable for landing.

Threshold crossing height - TCH - The theoretical height above the runway threshold at which the aircraft's glideslope antenna would be if the aircraft maintains the trajectory established by the mean ILS glideslope or the altitude at which the calculated glidepath of an RNAV or GPS approaches.

Track - The projection on the earth’s surface of the path of an aircraft, the direction of which path at any point is usually expressed in degrees from North (true, magnetic or grid).

Transition Level - The lowest flight level available for use above the transition altitude

Transition Layer - The airspace between the transition altitude and the transition leve.

Transition Altitude - The altitude at or below which the vertical position of an aircraft is controlled by reference to altitudes

True altitude - is the actual elevation above mean sea level

Touchdown - The point where the nominal glide path intercepts the runwa

Touchdown zone - The portion of a runway, beyond the threshold, where it is intended landing aircraft first contact the runway.

Touchdown zone elevation - TDZE - The highest elevation in the first 3,000 feet of the landing surface. TDZE is indicated on the instrument approach procedure chart when straight-in landing minimums are authorized.

Touchdown zone lights - TDZL - rows of white light bars (with three in each row) at 30 or 60 m (98 or 197 ft) intervals on either side of the centerline for 900 m (3,000 ft).