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

===== You don’t eclipse at will; it’s tied to specific particles and structures. The main ones you should actually care about: =====

====== - ár “our” → eclipsis ======
* bhur “your (pl)** → eclipsis
* a “their” → eclipsis

vs
* mo, do, a (his) → lenition (séimhiú)
* a (her) → eclipsis of vowels / h-prefix, but no eclipsis of consonants

Examples:
* bád “boat”: - ár mbád “our boat” - bhur mbád “your (pl) boat” - a mbád “their boat” - but mo bhád “my boat” (lenition, not eclipsis)
* athair “father” (vowel initial): - ár n-athair “our father” - a n-athair “their father” - a h-athair “her father” (h-prefixed, not n-)

====== With “na” + genitive plural, common pattern is eclipsis: ======
* fear “man” → na bhfear “of the men”
* carr “car” → na gcarr “of the cars”

Compare nominative plural:
* na fir “the men” (no mutation there), but teach na bhfear “the men’s house”.

====== Preposition i “in”, when combined with article, causes eclipsis: ======
* i + an → sa/san + eclipsis: - carr → sa gcarr “in the car” - bád → sa mbád “in the boat”

Also with plain i before vowels:
* i nGaillimh “in Galway”

You’ll see the same behaviour in extended forms like ins an, sna (pl.).

====== Numbers seacht, ocht, naoi, deich commonly cause eclipsis: ======
* cupla “a couple of”: no mutation.
* seacht gcapall “seven horses”
* ocht gcapall “eight horses”
* naoi gcapall “nine horses”
* deich gcapall “ten horses”

Earlier numbers (dhá, trí, ceithre) usually cause lenition instead.