Plurid is a term we coined to describe collective identities had by systems, or to label things that collectively affect the system's identity.
It is short for "plural identity", and while it can be synonymous with "collective identity", it can also describe the way things affect identity throughout a system or a part of a system.
It may be something that
-is very common among individual members
-is ascribed to the system's singletsona or the system presents as
-the system has lived experiences with or that their social circle is associated with
-that no individual member identifies with but that the system makes up collectively
A plurid may also be something that isn't necessarily an identity but can affect identity, such as experiences or interests.
A system who presents as a lesbian in person may be part of lesbian communities, both online and offline. They may participate in lesbian activism, make lesbian art, or be in a lesbian relationship (either with a singlet or a system). Not every member of that system may be a lesbian, but they are affected by living the identity of lesbian. Therefore, that system could be lesbianplurid, so as to explain why their non-lesbian headmates would still talk about knowing what it's like to be a lesbian.
A system who roleplays online often has a social circle associated with it, as roleplay is a social hobby. If they are openly plural, then their roleplay friends might talk to and befriend members of the system who do not roleplay. This system might also get introjects related to their roleplays, or headmates who contribute ideas to their roleplays without actively participating. Therefore, that system could be roleplayplurid, so as to explain how roleplay affects the entire system while not being a thing everyone in the system does.
A system who grew up feeling alienated from humanity might have related to cats instead of humans. As a result, they have a lot of headmates who are connected to cats. However, this includes talking cats as well as anthros as well as people with animal ears as well as otherkin as well as just headmates who like cats. They don't all relate to cats in the same way, but cats are collectively a part of the system's identity, so they could be catplurid.
When our system uses plurids to describe sidesystems or structures, that often has something to do with how that identity affected parts of our past. For example, parts of our system that are lesbianplurid are connected to our identity as a lesbian in the past, because those parts of the system are from the past.
Plurid is similar to a few other identity terms for systems. Here are some suffixes that are similar and different:
-plex: When something afffects the entire system, even if it's not in the exact same way. For example, addictionplex for a system collectively impacted by addiction. Plexes and plurids often overlap, but a plex term is not always an identity. Furthermore, some systems with plurids may not actually feel like all headmates are affected by that identity. However, they still feel that the collective is affected, even if not all individuals are.
-based: When something affects system functions, splits, and headspace, without necessarily being an origin. This is similar to how some plurids are not exactly collective identities but rather a description of how something affects identity in a system. This definition of plurid is like based terms, but saying that the system's collective identity is something-based, rather than that the system in general is something-based.