TransID (sometimes also called transX) is the umbrella term for identities such as transage, transabled, transspecies, diarace, and many other labels.
Though many people in the transID community are transgender, the concept is controversial in the wider transgender community.
Generally, transID people feel a disconnect between what their body is and what their mental image of themself is. A transabled person might feel unhappy when reminded of their limb that feels foreign to them (dysphoria). A transspecies individual might feel happy when in their natural environment (euphoria).
Often, transIDs intersect with plurality. Headmates/alters have been known to have internal appearances that are very different from the body they inhabit. Animal alters may resonate with the label of transspecies. Fictives of a different race than the body may identify as transracial. Someone might identify as transage because they are a system little.
TransIDs can intersect with trauma. Many transage people have a younger internal age because of trauma. Also, plurality is often shaped by trauma.
Though some transidentities are common, there are theoretically infinite microlabels people can use. Though I define each of these in one sentence, some people would define them differently.
Transspecies is a term for those who feel that their internal species does not match their body's.
Though it may be similar and have overlap with otherkin and therians, it is not exactly the same thing.
Common identities include: animals, fantasy species, cyborgs/computers/robots
Transage individuals feel that their internal age does not match their chronological age.
Transage people can feel that their internal age is younger, older, nonexistant (ageless), fluid... or anything, really.
Transabled was a term originally coined in 2004 by Seaon O'Connor as an shorter, neutral alternative to "[disability] wannabe" and "Body Integrity Identity Disorder Sufferer".
BIID is a condition in which someone feels that they should have an amputation (or paralysis) to an otherwise-healthy limb. They often feel that the limb isn't meant to be there, and feel relieved thinking about it being gone. It is different from psychosis or amputee fetishism. Some BIID sufferers get amputations - though this is dangerous, some have reported feeling relieved that they did it.
Source: biid-info.org/Transabled, some transabled studies I read earlier which I will cite when i get to it [todo]
This term has several names because the term "transracial" is already used for 'transracial adoptees' (adoptees with parents of a different race), so people have tried to come up with alternatives (trace/diarace). It is for people who feel that their race is different than the one that is assigned to them because of their heritage/genetics.
Though they are often stereotyped as only being White-to-Black or White-to-Asian, they can be transitioning to any race, and be of any genetics.