Mathematics · Glossary
What is Combination?
Quick definition
A selection of items where order does NOT matter. C(n,k) = n! / (k!(n-k)!).
Full explanation
A combination is a selection of items from a larger set where order does not matter. The number of ways to choose k items from n is C(n,k) = n! / (k!(n-k)!). Example: choosing 3 cards from a 52-card deck = 22,100 combinations. Combinations are the basis of the binomial theorem and probability calculations. They differ from permutations, where order matters. "How many ways to pick a 5-card poker hand" = 2,598,960 combinations. "How many 5-letter words" = 26P5 = 7,893,600 permutations. Choose combination or permutation based on whether order is meaningful in your problem.
Related calculators
Calculators that use or explain Combination.
Related terms
More from Mathematics
Standard Deviation
A measure of how spread out numbers are from their mean. Low = consistent, high = volatile.
P-Value
The probability of observing results at least as extreme as those observed, assuming the null hypothesis is true.
Mean (Average)
The sum of values divided by the count. The most common type of "average." Sensitive to outliers.
Median
The middle value in a sorted list. Half the values are above, half below. Robust to outliers.
Pythagorean Theorem
In a right triangle, the square of the hypotenuse equals the sum of the squares of the two legs: a² + b² = c².
Logarithm
The exponent to which a base must be raised to produce a given number. log(100) = 2 means 10² = 100.
Last reviewed: June 15, 2026 • Category: Mathematics