General Aviation aircraft experienced a runway incursion due at least in part to the new 'Line Up and Wait' phraseology.

Narrative

After a short stop at TKI en route from RBD to collect 2 passengers; aircraft was cleared by TKI Ground to taxi to the end of Runway 18. After run-up; TKI Tower gave instructions for aircraft to 'hold short' while another aircraft took off from an intermediate position on the runway. Pilot mistakenly thought he had been instructed to 'line up and wait'; and positioned on runway for takeoff. Tower ATC then gave normal clearance for takeoff some 30 seconds after the incursion. After arriving at destination; pilot phoned TKI Tower as instructed. On discussion of the incident; it was established that the incident had probably occurred due to confusion over terminology. A contributing factor may have been the recent change of US civilian ATC practice from the use of the phrase 'Position and Hold' to 'Line Up and Wait'. A further factor was the presence of a student pilot on board; whose desire to assist the pilot may have been a distraction. The Controller also admitted that at first he was unsure whether he had given the correct clearance; largely due to the recent change in terminology.