a quantity that does not vary
"The speed of light is a constant that remains unchanged regardless of where you measure it in the universe."
a number representing a quantity assumed to have a fixed value in a specified mathematical context
"the velocity of light is a constant"
That which is permanent or invariable.
"The constant hum of the refrigerator never goes away, no matter how late it gets at night."
In plain English: A constant is something that never changes or stays exactly the same no matter what happens around it.
"She relied on his constant presence during her recovery."
Usage: Use the noun "constant" to refer to an unchanging factor or principle that remains the same throughout a process. It is often paired with "variable" to describe something stable amidst changing conditions.
unvarying in nature
"maintained a constant temperature"
"principles of unvarying validity"
steadfast in purpose or devotion or affection
"a man constant in adherence to his ideals"
"a constant lover"
"constant as the northern star"
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"
Unchanged through time or space; permanent.
"The constant hum of the refrigerator never goes away, no matter how late it gets at night."
In plain English: Constant means something that happens all the time without stopping or changing.
"The constant noise from the construction site made it hard to concentrate."
Usage: Use "constant" to describe something that remains exactly the same over time, such as a steady temperature or an unchanging rule. Do not use it to mean frequent or numerous, which is the meaning of "constantly."
The word "constant" entered English through the Norman conquest via Old French and Latin, where it originally meant to "stand firm." This borrowing replaced an earlier native Old English term that had a similar meaning.