[Yahya A.Sharif (OP)]

Space increment per time means increment in distance per time or increment in velocity, velocity increment causes increment in mass causes more pressure on space-time causes increment in space-time density.

However increment in space per time itself is increment in space-time density.

Inertia is the rate at which  space resist pressure  " increment in mass"or the rate at which density increases.

Increment in space-time density resists motion

[Bored chemist]

None of that makes much sense.