constant

nouns

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"
is a type of (narrower)
a concept of quantity involving zero and units
"every number has a unique position in the sequence"

adjectives

unvarying in nature
"maintained a constant temperature"; "principles of unvarying validity"
is derived from
steadfast in purpose or devotion or affection
"a man constant in adherence to his ideals"; "a constant lover"; "constant as the northern star"
is derived from
antonym
is similar to
firm and dependable especially in loyalty
"a steadfast ally"; "a staunch defender of free speech"; "unswerving devotion"; "unswerving allegiance"
is similar to
unceasing
"unfailing loyalty"; "unfailing good spirits"; "unflagging courtesy"
see also
not changeable or subject to change
"a fixed and unchangeable part of the germ plasm"-Ashley Montagu; "the unchangeable seasons"; "one of the unchangeable facts of life"
see also
steadfast in affection or allegiance
"years of faithful service"; "faithful employees"; "we do not doubt that England has a faithful patriot in the Lord Chancellor"
see also
resistant to change of position or condition
"a stable ladder"; "a stable peace"; "a stable relationship"; "stable prices"
see also
not liable to or capable of change
"an invariable temperature"; "an invariable rule"; "his invariable courtesy"
is an attribute of
the quality of being enduring and free from change or variation
"early mariners relied on the constancy of the trade winds"
uninterrupted in time and indefinitely long continuing
"the ceaseless thunder of surf"; "in constant pain"; "night and day we live with the incessant noise of the city"; "the never-ending search for happiness"; "the perpetual struggle to maintain standards in a democracy"; "man's unceasing warfare with drought and isolation"; "unremitting demands of hunger"