No single written definition of "polyamory" has universal acceptance. It is generally agreed that polyamory involves multiple consensual, loving relationships (or openness to such), but beyond that the term is as ambiguous as the word love itself.
Some object to the idea that one must currently be participating in multiple relationships to be considered polyamorous. Others would consider their relational outlook polyamorous, regardless of whether they happen to be single or in an exclusive relationship at the time. A relationship is more likely to be called "polyamorous" if at least one relationship is long-term, involves some sort of commitment (e.g. a formal ceremony), and involves shared living arrangements and/or finances, but none of these criteria are necessary or definitive.For instance, somebody who has multiple sexual partners might form strong loving friendships with them, without feeling romantic love for them. Whether such a person identifies as "polyamorous", or as a swinger, or uses some other term, often depends more on their attitude towards other "polyamorists", "swingers", etc., than on the exact nature of their relationships. Different terms emphasise different aspects of the interaction, but "swinging" and "polyamory" are both broad in what they can refer to. This allows for a certain degree of overlap.
Similarly, an open relationship in which all participants are long-term friends might be considered "polyamorous" under broader usages of the word but excluded from some of the tighter usages (see further discussion below). There is enough overlap between these concepts that the expression "open relationship" is also sometimes used as a catch-all substitute when speaking to people who may not be familiar with the term "polyamory". However, some have objected to this shorthand, on the basis that multiple partners does not necessarily imply that they also have open relationships.