Relationship that connects elements that are similar by one of their properties.

- In the case of relationships between units of measurement, it is acceptable to use the symbol =.

However, when reading them, it is preferable to use the expression “is equal to” or “is equivalent to”. - So, for 1 m = 100 cm, we would say that one metre is equivalent to one hundred centimetres.

### Examples

- The relationship “…has the same parity as…” in the set of divisors of 64 is an equivalence relationship.
- The relationship “…is parallel to…” in the set of lines on graph is an equivalence relationship.
- The fractions \(\dfrac{6}{9}\), \(\dfrac{10}{15}\), \(\dfrac{14}{21}\) and \(\dfrac{20}{30}\) are equivalent, because they are all equivalent to the fraction \(\dfrac{2}{3}\).
- The units of measurement “1 m” and “100 cm” are
**equivalent units of measurement**. - The relationship “…is perpendicular to…” in the set of lines on a graph
**is not an equivalence relationship**.