1C1

1C1 is most commonly encountered as a binomial coefficient, commonly written as 1C1 or C(1,1). It denotes the number of ways to choose one item from a set of one, and its value is 1. The binomial coefficient is usually written nCk or C(n,k) and is defined as n!/(k!(n−k)!). In the case of 1C1, the computation gives 1!/(1!0!) = 1. Combinatorially, 1C1 counts the selections of a single item from a one-item collection, which is exactly one possibility. The concept is used in formulas such as the binomial theorem, where (x+y)^n expands into a sum of terms with coefficients nCk.

Aside from mathematics, 1C1 may appear as an alphanumeric identifier in product codes, model numbers, or catalog references across industries. Without context, the meaning is not fixed. When encountered in documentation, surrounding text or a specification sheet usually clarifies whether 1C1 refers to a binomial coefficient or to a specific item designation. In computing and engineering, codes like 1C1 can denote components, revisions, or version identifiers, but there is no universal standard. The use of such codes is highly context-dependent.