Open relationship is a term which refers to a mate relationship which is not entirely monogamous, but allows for sexual encounters with others, or even ongoing relationships. This form of relationship is a common occurrence within the furry fandom, perhaps due to analogy with or imitation of non-monogamous behaviour among other animal species. However, such a form of relationship is not exclusive to furry, nor can it be said to represent the majority of relationships in the fandom.
The term open relationship is sometimes used more broadly to include polyamory. However, it is usually used in contrast, referring to an emotionally monogamous relationship which is not sexually exclusive. As such, sex is sometimes considered more as a recreational activity rather than a key foundation to the relationship.
Open relationships are especially common when a relationship is online or long-distance.