stable

stable adjective abiding, anchored, chronic, constant, continuing, deep-rooted, diligent, durable, endless, enduring, established, everlasting, faithful, fast, fastened, firm, firmus, fixed, grounded, immovable, immutable, indissoluble, indomitable, industrious, inert, intact, invariable, inveterate, irremovable, irrevocable, lasting, long-lasting, long-lived, long-standing, moored, motionless, perdurable, perpetual, persistent, plodding, relentless, reliable, riveted, rooted, secure, sedulous, settled, solid, sound, stabilis, stalwart, stanch, stationary, steadfast, steady, strong, sturdy, substantial, sure, tenacious, unalterable, unchanging, uncompromising, undeviating, unfailing, unfaltering, unflagging, unflinching, unhesitating, unremitting, unshakeable, unshaken, unswerving, untiring, unwavering, unyielding, well-built, well-grounded

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See also: certain, constant, demonstrable, dependable, durable, firm, fixed, indelible, indomitable, infallible, irrevocable, permanent, perpetual, rational, regular, reliable, secure, solid, sound, static, staunch, steadfast, strong, unalterable, unyielding