Moment (noun)

1. A very brief period of time.
2. A particular point in time.
3. A unit of measurement of the force acting on an object for a given period of time.

Origin:

From the middle english moment, from the old french moment, from latin momentum, from movēre ("to move").

Examples:

1. I'll be there in a moment.
2. At the moment, he was sound asleep.
3. The moment of truth has arrived.
4. The moment of the rocket launch was spectacular.
5. The moment of inertia of the system is a measure of its resistance to angular acceleration.