The "Elfae Spectrum"
Elves, Sidhe, Faery, Tuatha
by Arethinn

Well, that sounds confusing, doesn't it? Related, similar, but not the same thing... except when we are! (*evil grin*) The roots of today's general otherkin community are mainly traceable back to forays online in the early 1990s by elven folk looking for others like themselves. It soon became apparent that there were a lot of things out there that might be calling themselves "elves", and often they used one or more of the other words above as well.
For this section, please keep the following three things in mind:
1. When I mention elves, I am generally talking about Earth-natives. I am acquainted with a number of "space elves" who came here from other worlds, and clearly there is a resemblance of "feel" which leads them to use the same word for themselves, but statements about relationships to fae, for example, might not apply.
2. I consider elves, fae, sidhe, and Tuatha De Danann to all be distinct things, although there are definitely similarities and overlaps and in some cases hybrids between them. (However, when I say "elfae" or "elfaesidhe" I am not referring to hybrids, but using the words as a grouping term to collectively refer to the whole spectrum at once; my pal Andros, on the other hand, uses a term in the reverse order Faelf -- fae-elf -- for himself and does mean a hybrid.) Other people, both within and without the otherkin community, may use two or more of those terms interchangeably or consider some of them to be subgroups of others.
3. Fae are not the same as nature spirits or elementals, although there are similarities and overlaps here as well: some fae have a strong elemental connection, or are linked to a particular place or kind of plant, for instance.
My own thoughts on this have changed over time, becoming both more broad and more narrow (or more permissive and more restrictive) at different points. Currently (2021), speaking only of beings on Earth since that's mostly what I know: I think fae, (Earth-born) elves, and sidhe are distinct at least as much as breeds of cats or dogs are distinct and quite possibly moreso, but it's also possible we all come from a single "root race" or common ancestor, though that could be quite far back in history (similar to how humans' and chimpanzees' common ancestor is some millions of years ago). I'm not sure whether the Tuatha are outsiders or not, but lean towards the idea that they are, and became intermingled with the sidhe who already resided here, so that from a current perspective they are something like a specfic grouping of sidhe that are differentiated somewhat from the rest. (I'm sure some Tuatha out there could offer me some Opinions on this. ;) )
One of the reasons the whole elven-faery spectrum is muddled is that "elf", "fae/fairy/faery" and "sidhe" are all words from different languages for what might possibly be all the same general sort of being. Now, when I say "all the same", that doesn't mean "identical" - I mean "all the same" somewhat like the way in which humans are all the same. That is to say, there is still a wide spectrum of difference. Elves, fae and sidhe are related, IMO, but the words are not interchangeable (at least not anymore - language evolution and all that) and descirbe different "essences".
So what exactly distinguishes the "sidhe essence" from the "elven essence" from the "faery essence"? Again IMO, I think there is a spectrum or Venn-diagram thing going on here. My feeling is that sidhe is in between faery and elven, faery having the more wild, primal, chaotic feel, the relation to pure Glamour and the all-possibility of "Dreaming" (to use a Changeling term); elves tend to be refined, civilized, "crystalline" (this word describes their feel to me but makes a lot of people raise their eyebrows), even your "wild" tribes or types. Sidhe partake of both these essences - hence the idea of the warrior-fae who are masters of skills and built great cities and like that.
This leads into Tuatha de Danann, which are kind of their own thing, but again there is some kind of relation. If they do not call themselves "Tuatha" then the next most common word I see them use for themselves is "sidhe"; somewhat less common, "elf". This connection/identity with Tuatha is the main reason I used to hesitate to use the word "sidhe" for myself, because while I might feel a link to Dana herself, the whole Tuatha thing has never yet held any resonance of possible identity for me. I've become more comfortable with "sidhe" over the past ten years or so, whereas I used to default to "faery", but I still do use the latter word as well. One of the things that the word "sidhe" carries for me is "shining". Faery doesn't necessarily have this - there are a lot of faery races that are not "shining ones", and elves sort of quietly glimmer. Sidhe are radiant. (I think this might be a point of connection/conflation with angelic types, actually.)
So given all of this, I lumped all four things together here rather than trying to put them in more specific categories, because otherwise I'd have to agonize over which category a given link fit best. While I might like to do that in my personal bookmarks, it seems silly to do it on a public website where I'd rather make it easier for people to just find stuff, yanno?
Below are a couple of relevant posts I've made on the topic of this spectrum of interrelated kindreds:

January 2004, list or forum unknown
Re: Tuatha as fae... While I think it is reasonable to apply the adjective "faery" to (at least some) Tuatha de Danann, IMO that comes from the fact that their lands under the hills could be considered Faery lands... extensions into this world of the "mirror image" world that is Faerie. However, I would not call them "faeries".
Re: Dannan energy coming across as gold... I saw someone talking about this on Enchanted Realms, and also a number of people on FAE seem to feel the same way. A common perception. Like Lann, I also associate a kind of silvery feel with sidhe, but I associate it (or a similar one) with elves as well... something almost crystalline, whereas Tuatha has that golden feel, and Faerie is... multicoloured, or multicoloured iridescence on top of green... with maybe some gold in it as well.
A simple physical difference is that elves rarely possess wings, whereas faeries very frequently do. I would say that sidhe would be somewhere in the middle, and also that they are less likely to have a physical nature, but rather to be an energetic feature... an extension of their "shining", a tattoo of light written on the air, if you like.

January 2004, list or forum unknown
I like to picture a spectrum:
Elves - Sidhe - Faery
Where exactly the Tuatha de Danann (and indeed, angelics - for various reasons people often perceive connections between angels and elves, or angels and fae) fit on this, whether they can be considered a kind of sidhe or are really a separate category, is not something I'm considering here. I have no subjective experience of that, myself, and it's often led to confusion on my part, because most of the other sidhe-types I know have a strong connection to Tuatha-ness that I just don't feel. (Dan O'Dea describes it as "Danaan gold", in reference to how he perceives the particular energy of Tuatha-sidhe.)
In any case, I feel that the three broad types are related, but certainly not interchangeable. And of course, where you have things like this, you would have people that fit firmly into one, and others that fit into the "borderlands" between. It might even be better to describe this as a circle, so Faery wrapped back around to Elves. In any case, I agree that sidhe are much like fae, especially in that they possess/use glamour, and tend to hail from places in Faerie, but there are fae that are completely non-sidhe as well.

And lastly, some comments from the Silver Elves, who coined the word "Elfae" as a collective term for we various Folke of Elven-Faƫrie:
Can One Be Both an Elf and a Faerie?
What's the Difference Between Elves and Fae?
Last updated 8/06/2021