# Constant

Pronunciation: /ˈkɒn.stənt/ Explain

A constant is a value that does not change.[1] It can also be a letter that represents a value that does not change.

### Examples

1. pi or π is used to represents the ratio of the circumference of a circle to its diameter. Since π always has the same value, it is a constant.
2. In the expression 2 + y, the 2 is a constant value.
3. In the linear equation y = m·x + b, both m and b represent values that do not change.

### Commonly Used Constants

• Zero, a = 0, 0 + a = a
0
• One, a = 1
1
• π, the ratio of the length of the circumference of a circle to the diameter.
π ≈ ˜3.14159265358979323846264338327950288
• Euler's number, the base of the natural logarithm.
e ≈ ˜2.71828182845904523536028747135266249
• Phi, the golden ratio.
φ = (1+square root(5))/2 ˜≈ 1.61803398874989484820458683436563811
• i, the imaginary unit.
i = square root of -1.

### References

1. McAdams, David E.. All Math Words Dictionary, constant. 2nd Classroom edition 20150108-4799968. pg 44. Life is a Story Problem LLC. January 8, 2015. Buy the book
2. Kornegay, Chris. Constant. 2nd edition. pg 72. Math Dictionary With Solutions: A Math Review. Sage Publications, Inc. March 6 1999. Last Accessed 6/25/2018. Buy the book
3. Bettinger, Alvin K. and Englund, John A.. Algebra and Trigonometry. pp 53-54. www.archive.org. International Textbook Company. January 1963. Last Accessed 6/25/2018. http://www.archive.org/stream/algebraandtrigon033520mbp#page/n70/mode/1up/search/constant. Buy the book

McAdams, David E. Constant. 4/16/2019. All Math Words Encyclopedia. Life is a Story Problem LLC. https://www.allmathwords.org/en/c/constant.html.

### Revision History

4/16/2019: Updated equations and expressions to new format. (McAdams, David E.)
12/21/2018: Reviewed and corrected IPA pronunication. (McAdams, David E.)