I

I translates to "in". It is used to indicate location, states of being (roles/actions), existence, and time.

Preposition Conjugated Dative

Overview

Pronoun	Form	Contrast Form	Translation
I	ionam	ionamsa	in me
You	ionat	ionatsa	in you
He	ann	annsan	in him / in it
She	inti	intise	in her
We	ionainn	ionainne	in us
You (pl)	ionaibh	ionaibhse	in you
They	iontu	iontusan	in them

The pronunciation of i is a short schwa [ə], not [i].

Base I + Ceanada

Mutated I gCeanada

Rule Eclipsis

Base I + an + siopa

Mutated Sa siopa

Rule Lenition (Standard)

I: Used before consonants (causes eclipsis).
In: Used before vowels (in Éirinn), numbers like dhá (in dhá bhróig), and titles (in “Cré na Cille”).
Sa: The combined form of i + an (Standard: lenites).
Ins/Is: Used in dialects before gach (every) or uile (all), e.g., ins gach bliain (in every year).

General Rule — i gCeanada — in Canada — i causes eclipsis on nouns without the article.
Vowel Rule — in Éirinn — in Ireland — Before vowels, i becomes in and causes no mutation.
With the Article — sa Ghearmáin — in Germany — i + an becomes sa. In the Standard, this causes lenition.
- Connacht Dialect: sa nGearmáin — Causes eclipsis (except on d, t).
- Munster Dialect: sa bhfarraige — Causes lenition, but f is eclipsed.

Question	Meaning	What happens next?	Example
Cé + i	In whom?	`Indirect`	Cé ann a bhfuil an locht?
Cad + i	In what?	`Indirect`	Cad ann atá sé?

Irish often describes what you “are” or what you are “doing” as a state you are “in”.

Actions (Progressive State) — tá mé i mo chodladh — I am asleep — Lit. “I am in my sleeping”.
Roles (Classification) — tá mé i mo dhochtúir — I am a doctor — Lit. “I am in my doctor-ing”.
- Tá tú i do fhear anois — You are a man now — Lit. “You are in your man-ness now”.
Becoming — éireoidh mé i mo dhochtúir — I will become a doctor — Lit. “I will rise into my doctor-ing”.

Existence — tá teach ann — there is a house — Lit. “A house is in-it”.
Adverbs — anseo (here), ansin (there/then), ansiúd (yonder) — Derived from ann + demonstrative.
- Note: annsan (in him) is distinct from ansin (there).

Location — sa phota — in the pot.
Relative Position — i mbun (at the bottom/foundation), in imeall (at the edge).
Time — san oíche — in the night / at night.
Rate — deich bpunt sa lá — ten pounds a day (per day).

Inherent Quality — maith i leabhar — good in a book (goodness found within it).
Internal Trait — sláinte sa ngrian — health in the sun.
Emotional State — i bpian — in pain; in imní — in anxiety.
Membership — sna Gardaí — in the Guards (Police); i mbanna — in a band.
Capability — in ann — able to / capable of.
Distribution — fear san fhear — man by man / man for man.