Meaning & use
a constant
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Meanings
nouncountabletechnicalmathematics
a number or quantity that does not change in a particular mathematical or scientific situation
Grammar: Used as a countable noun, often with 'the' when referring to a specific known value.
Patterns
- a constant in an equation
- a mathematical constant
- hold something constant
In the equation y = 3x + 5, the number 5 is a constant.
The speed of light is a physical constant that appears in many formulas.
Scientists treat the mass of the object as a constant during the experiment.
nouncountable
something that stays the same and does not change over time
Grammar: Often used in the phrase 'a constant in life' or 'the only constant'.
Patterns
- a constant in someone's life
- the only constant
- remain a constant
Her support was a constant during a difficult year.
Change is the only constant in the fashion industry.
He said that his love for music had been a constant since childhood.
Word forms
| plural | constants |
|---|
Common combinations
- a mathematical constant
- Pi is a mathematical constant used to find the area of a circle.
- a physical constant
- The gravitational constant is a physical constant.
- remain constant
- The temperature remained constant throughout the night.
- the only constant
- In this city, traffic is the only constant.
Synonyms and how they differ
- fixed value
- This is a more general term and can be used outside mathematics; 'constant' is the precise term in science and math.
- invariable
- This is an adjective or a formal noun meaning something that never changes; it is less common than 'constant' in everyday speech.
Opposites
Word family
- constant adjective
- staying the same over time; not changing
- constantly adverb
- continuously or very often
- constancy noun
- the quality of staying the same or being loyal
Commonly confused: a constant or variable? a constant or consistent?
a constant vs variable
A variable is a quantity that can change, while a constant stays the same. In an experiment, you might keep one thing constant and let another be a variable.
a constant vs consistent
This adjective means always behaving or happening in the same way, but it describes a pattern, not a fixed number or fact.
Practice
In the expression '2x + 7', what is the constant?
Choose one answer.
A constant is a value that does not change. In '2x + 7', the number 7 stands alone and never changes, while 2 is a coefficient and x is a variable.
Make it your own
Write a sentence using “a constant”, then check it and compare it with the examples above.