adjective

occurring continuously over a period of time.

the constant background noise of the city

continual,continuous,persistent,sustained,abiding,round-the-clock,ceaseless,unceasing,perpetual,incessant,never-ending,everlasting,eternal,endless,unending,unabating,non-stop,perennial,unbroken,uninterrupted,unrelieved,interminable,unremitting,relentless,unrelenting,without respite,sempiternal,steadfast,steady,resolute,determined,persevering,tenacious,dogged,unwavering,unflagging,unshaken

noun

a situation that does not change.

the condition of struggle remained a constant

unchanging factor,unchanging state of affairs,unchanging situation,given