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

=== Assistant: 2511132017ET ===
251113_2017ET

short version: in uisce, the u is part of the vowel /ɪ/; it is not there to broaden any consonant in that word. In other words, the same u can indeed serve mainly as a “broadness marker” for a consonant, but that’s a different pattern (e.g. buí).

===== Spelling: u i s c e =====
Modern standard: /ˈɪʃcə/

Segment-by-segment:
* ui → /ɪ/ - Think of ui as a digraph here: one short vowel phoneme /ɪ/. - The i also helps pull s into the slender zone → [ʃ].
* s is slender via i → [ʃ].
* c is slender via e → [c]/[kʲ] ~ [k].
* e is the reduced /ə/ of the second syllable.

So for uisce:
* u is part of the vowel; without it you wouldn’t get the “right” /ɪ/ in the historical/orthographic system.
* It is not doing any broad/slender job for a consonant here (no consonant before it; s is ruled by i, and c by e).

Historically, the vowel was closer to /u, ʊ, ɪ/ at various stages; the spelling ui is a conservative way of writing that old quality, which has settled as /ɪ/ in Standard.

===== Different pattern: C + u + slender vowel, where: =====
* u keeps the consonant broad,
* the slender vowel after that is the real vowel.

Classic example:
* buí “yellow” /bˠiː/ - b u: u keeps b broad. - í = actual vowel /iː/. - Here u basically has no vowel sound of its own in many speakers; it’s acting as a broadness buffer.

You see this kind of “pure broadener” role in various paradigms and loan spellings.

===== : =====
'' In ''uisce*, u is not just a broadness marker. It’s part of ui → /ɪ/, the main stressed vowel.
* In other words/contexts, u can act mainly or even purely as a broad marker (like in buí), but that’s not what’s happening in uisce.