# Dependence relation

In mathematics, a **dependence relation** is a binary relation which generalizes the relation of linear dependence.

Let be a set. A (binary) relation between an element of and a subset of is called a *dependence relation*, written , if it satisfies the following properties:

- if , then ;
- if , then there is a finite subset of , such that ;
- if is a subset of such that implies , then implies ;
- if but for some , then .

Given a *dependence relation* on , a subset of is said to be *independent* if for all If , then is said to *span* if for every is said to be a *basis* of if is *independent* and *spans*

**Remark.** If is a non-empty set with a dependence relation , then always has a basis with respect to Furthermore, any two bases of have the same cardinality.

## Examples

- Let be a vector space over a field The relation , defined by if is in the subspace spanned by , is a dependence relation. This is equivalent to the definition of linear dependence.
- Let be a field extension of Define by if is algebraic over Then is a dependence relation. This is equivalent to the definition of algebraic dependence.

## See also

*This article incorporates material from Dependence relation on PlanetMath, which is licensed under the Creative Commons Attribution/Share-Alike License.*