constant

Uninterrupted in time and indefinitely long continuing.

“in constant pain”

Unvarying in nature.

“maintained a constant temperature”

Steadfast in purpose or devotion or affection.

“a man constant in adherence to his ideals”

“a constant lover”

A quantity that does not vary.

A number representing a quantity assumed to have a fixed value in a specified mathematical context.

“the velocity of light is a constant”