What Does “T-Minus” Mean?

The term ‘T-minus’ is generally used during countdowns to space launches. During a NASA countdown to a rocket launch, ‘T-minus’ translates to ‘Time minus’; the ‘T’ stands for the exact time at which the rocket is scheduled to be launched.

The closer the time of launch approaches, the more the countdown will be “T-minus 9 hours,” “T-minus 5 hours,” “T-minus 55 minutes,” etc., until it reaches the most iconic part of the launch countdown – the last 10 seconds before launch. At this point, the announcer says, “T-minus 10, 9, 8…. 3, 2, 1 and take off!”

However, there are pre-planned holds in the countdown process, during which time the T-time is also stopped. Thus, the T-time can be stopped according to pre-planned holds in the launch procedure.