What does constant mean?
'Constant' functions primarily as an adjective meaning unchanging, continuous, or persistently present over time. It can describe something that happens repeatedly without interruption, such as 'constant rain' or 'constant interruptions', as well as something that remains at the same level or value, such as 'a constant temperature' or 'a constant speed'. A secondary, older sense describes someone loyal and steadfast in affection or commitment — 'a constant friend' — though this usage is now somewhat literary. As a noun, 'constant' refers chiefly to a fixed quantity that does not vary, especially in mathematics, physics, and computing: the speed of light and the gravitational constant are famous examples. The word carries a largely neutral tone but often connotes persistence or relentlessness when describing nuisances, and reliability or stability when describing conditions. It derives from Latin 'constans', meaning standing firm, and remains a versatile, high-frequency term in both everyday and scientific English.
Continuously occurring, remaining the same, or persistent over time; also, faithful and unwavering.
"The region suffers constant power cuts during the dry season."
Distinguish between the temporal sense (continuously happening) and the static sense (unchanging in level).
A quantity, value, or factor that remains fixed and unchanging, especially in mathematics or science.
"In the equation E = mc², c represents a physical constant — the speed of light."
The plural applies only to the noun sense, typically referring to multiple fixed values in mathematics or science.
"The formula depends on several known constants, including the gravitational constant."
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of constant
'Constant' comes from Latin 'constans', the present participle of 'constare', meaning 'to stand firm' or 'to stand together', formed from 'com-' (together) plus 'stare' (to stand). The word entered Middle English around the 14th century via Old French, initially carrying strong senses of steadfastness and fidelity before broadening to its modern meanings of continuity and invariance. It shares this Latin root with words such as 'constancy' and 'constantly'.
How constant is actually used
As an adjective, 'constant' can describe both uninterrupted duration ('constant noise') and unchanging state ('a constant temperature'), so context determines which nuance is meant. It is neutral-to-formal in register and common in both everyday speech and technical writing.
Easily confused with constant
'Consistent' means free of contradiction or reliably behaving in the same way across instances, while 'constant' means unchanging or continuously present over time.