Synonyms for Constant:

adj.

abiding (adjective)
enduring.
all (adjective)
changeless, unvarying, invariant.
continuing (adjective)
unending.
continuous (adjective)
endless, interminable, sequential, continuing, everlasting, level, seamless, continuous, unchangeable, perpetual, undeviating, featureless, perennial, steady, invariable, nonstop, unbroken, lasting, consecutive, incessant, undying, cyclical, monolithic, unchanging, connected, un-intermittent, straight, homogeneous, even, repetitive, regular, repeated, flat, indefatigable, uniform, unceasing, recurrent, unremitting, persistent, robot-like, gapless, coherent, unending, unvarying, habitual, consistent, continual, monotonous, ceaseless.
fixed (adjective)
stable, homogeneous, monotonous, unvarying, perpetual, nonstop, firm, uniform, immutable, even, connected, steady, unbroken, regular, unchanging, permanent, invariable, habitual, continual, equable, consistent, uninterrupted, standardized, steadfast.
frequent (adjective)
frequent.
habitual (adjective)
repeated, habitual.
infinite (adjective)
interminable.
irrevocable (adjective)
irreversible.
liege (adjective)
liege.
loyal, determined (adjective)
persevering, unwavering, unflagging, true, allegiant, resolute, dogged, devoted, trustworthy, fast, staunch, faithful, unfailing.
never-ending (adjective)
undying, ceaseless.
neverending (adjective)
chronic, unremitting, lasting, interminable, abiding, continuous, eternal, enduring, endless, incessant, unending, persistent, ceaseless, everlasting, relentless.
permanent (adjective)
enduring, permanent, perpetual, everlasting, unchangeable, persistent, lasting, changeless, abiding, immutable, fixed.
perpetual (adjective)
immortal, ceaseless, infinite, everlasting, incessant, uninterrupted, unceasing, continual, endless, interminable, lasting, permanent, enduring, eternal.
regular (adjective)
common, steady, canonical, mundane, general, prevailing, orthodox, customary, normal, recurrent, frequent, chronic, habitual, routine, ordinary, Predominating, average, metronomic, regular, traditional, rhythmic, commonplace, standard, everyday, conventional, periodic, continual, usual, cyclical, monotonous, Familiar, epochal, accustomed, universal, stock.
resolute (adjective)
dedicated, insistent, plucky, committed, bold, zealous, unflinching, ruthless, serious, decisive, loyal, indomitable, steady, earnest, set, implacable, deliberate, iron-willed, fearless, strong-willed, decided, resolved, resolute, unwavering, tireless, valiant, relentless, reliable, uncompromising, determined, willing, unchangeable, bullheaded, thorough, steely, diligent, headstrong, inexorable, tenacious, courageous, unyielding, hearty, stubborn, firm, spunky, devoted, tough, strong-minded, intent, true, stern, indefatigable, staunch, persevering, persistent, faithful, dauntless, unbending, dogged, steadfast, unshakeable.
stable (adjective)
durable, stable, immovable, invariable, permanent, solid, steady, consistent, continuous, persistent, set, steadfast, firm, changeless.

n.

final, equable, standardized, irreversible, for good, rigid, whatever happens. extended, timeless, around the clock, long, on and on, round the clock, prolonged, for some time, continue, ongoing, long-term. arithmetic progression, computation, cube, base, same, cube root, common multiple, common factor, Arabic Numeral, coefficient, change. darn, for heaven's sake/sakes, what's the big idea?, brother, for crying out loud, give me a break, give me strength, what's that supposed to mean?, for pity's sake. stiff, purpose, done deal, a done deal, fait accompli. allegiant, trust, fast, liege. cognition (noun)
invariable, constant quantity.
constant (noun)
constant quantity, perpetual, continuous, unflagging, continual, unremitting, steady, unswerving, unceasing, incessant, unvarying, changeless, ceaseless, never-ending, invariant, uninterrupted, steadfast, unfailing, staunch.
loyal (noun)
diehard, trustworthy, stalwart.

Other synonyms:

arithmetic progression, allegiant, fait accompli, rigid, round the clock, Arabic Numeral, common factor, coefficient, common multiple, extended, timeless, equable, cube root, prolonged, final, done deal, around the clock. liege, cube, long-term, ongoing, computation. stiff, same. long. base. fast. loyal
stalwart, diehard.
unchangeable
irreversible.
Other relevant words:
stalwart, invariant, long-term, round the clock, rigid, never-ending, equable, unflagging, irreversible, diehard, allegiant, timeless, trustworthy, same, unfailing, ongoing, liege, fast, computation, constant quantity, coefficient, unswerving, standardized, stiff.

Usage examples for constant

  1. " I hoped more from Leo's constant companionship, and from his influence over his uncle. – Under a Charm, Vol. II. (of III) A Novel by E. Werner
  2. He said he could stand your father by constant prayer, but he gave notice over Charles. – The Dark Tower by Phyllis Bottome