Editing Openai/69186d20-2d14-8013-b9c6-c09000f173f6 (section)

=== Assistant: 2511141839ET ===
251114_1839ET

P- vs Q-Celtic is about one big sound change; Insular vs Continental / Goidelic vs Brythonic is the fuller family tree. I’ll separate those.

==== It’s defined by the reflex of Proto-Indo-European *kʷ (a labialized velar, like [kʷ]): ====
'' Q-Celtic: ''kʷ stays [k]/[kʷ], written c / qu → “Q”
'' P-Celtic: ''kʷ > p → “P”

Classic example: “four”
'' PIE ''kʷetwóres
'' Q-Celtic (Irish): ceathair /ˈcahəɾʲ/ (c- from ''kʷ-)
'' P-Celtic (Welsh): pedwar (p- from ''kʷ-)

Another stock example: “horse”
'' PIE ''h₁eḱwos
'' Q-Celtic (Old Irish): ech (e-ch from ''ekw-)
* P-Celtic (Gaulish): epo- (in names like Eporix), Welsh ebol “foal” (same p-).

So:
'' Q-Celtic = languages where ''kʷ is still “k-like” → Goidelic + Celtiberian.
'' P-Celtic = languages where ''kʷ has merged into p → Brittonic (Welsh, Cornish, Breton) + Gaulish.

The “Q” label comes from Latin spelling: Q was used for [kʷ], so “Q-Celtic” = “kept the [kʷ]-type reflex”.

==== ### ====
* Goidelic (Insular) - Irish (Old Irish, Modern Irish) - Scottish Gaelic - Manx
'' Celtiberian (Continental) - Ancient language of central Iberia, known from inscriptions; also shows ''kʷ > k/qu rather than p.

So Q-Celtic = Goidelic + Celtiberian.

===== - Brittonic (Insular) - Welsh - Cornish - Breton =====
* Gaulish (Continental) - Ancient Celtic of most of what is now France / N. Italy.

So P-Celtic = Brittonic + Gaulish.

Note how this cuts across geography:
* Insular: both Q (Goidelic) and P (Brittonic)
* Continental: both Q (Celtiberian) and P (Gaulish)

So P/Q is not a simple Insular vs Continental split; it’s one sound isogloss that bisects the family.

==== The standard genealogical picture you actually want in your head: ====
# Continental Celtic (all extinct) - Gaulish (P-) - Lepontic - Celtiberian (Q-) - Galatian (in Anatolia)
# Insular Celtic (survivors + some extinct) - Goidelic (Q-Celtic) - Irish - Scottish Gaelic - Manx - Brittonic (P-Celtic) - Welsh - Cornish - Breton

Within Insular Celtic, there’s also a strong view that all Insular languages share innovations beyond P/Q (syntax, verbal periphrasis, mutations, etc.), so many linguists treat Insular Celtic itself as a real subgroup, and P/Q as a secondary isogloss inside it plus its Continental echoes.

A related proposal is Gallo-Brittonic:
* Gaulish + Brittonic share various extra traits (including P-feature) → some people posit a Gallo-Brittonic subgroup (Gaulish + Brittonic) vs Goidelic + Celtiberian as another cluster.

So your hierarchy of “types” looks roughly like:
* Celtic - Insular Celtic - Goidelic (Q) - Brittonic (P) - Continental Celtic - Gaulish (P), Celtiberian (Q), etc.

with P/Q running diagonally across.

==== Important nuance: ====
* P/Q is based on one sound change, albeit a big, clean one.
'' It’s great for quick typologizing and for certain etymological comparisons: - ''kʷetwóres → ceathair vs pedwar - *h₁eḱwos → ech vs epo- / ebol
* But it’s not a complete phylogeny: - It doesn’t encode all the shared innovations (especially syntactic/morphological ones). - It can be cross-cut by other areal and genealogical patterns (Insular vs Continental, Gallo-Brittonic, Italo-Celtic, etc.).

So: use P/Q as “diagnostic sound law label”, and Insular/Goidelic/Brittonic/Continental as your actual family structure.

If you’d like, next I can take a single PIE root with *kʷ and walk it systematically through: Proto-Celtic → Goidelic vs Brittonic vs Italic vs Germanic, so you can see the full reflex set side-by-side.