Prepositions with the Article in Irish

Overview

When a simple preposition meets the definite article an in Irish, they often merge into a single combined form. These combinations are essential for everyday speech — you cannot simply place a preposition and article side by side as separate words in most cases. Each combined form triggers specific mutations on the following noun.

The most common combinations include sa/san (in the), den (of the/from the), don (to the/for the), ón (from the), and leis an (with the). Some of these fuse completely into one word, while others remain as two words but still trigger mutations. Learning these combinations is a major step toward natural-sounding Irish.

The mutations triggered by these forms follow patterns: sa causes lenition (in most cases), while leis an, ag an, and ar an cause eclipsis in the standard language. These mutation rules may vary between dialects, but the standard patterns are what you should learn first.

How It Works

Combined Forms

Preposition	+ an	Combined Form	English
i (in)	an	sa / san	in the
de (of/from)	an	den	of the / from the
do (to/for)	an	don	to the / for the
ó (from)	an	ón	from the
faoi (under/about)	an	faoin	under the / about the
le (with)	an	leis an	with the
ag (at)	an	ag an	at the
ar (on)	an	ar an	on the
as (out of)	an	as an	out of the
trí (through)	an	tríd an	through the
roimh (before)	an	roimh an	before the

Mutations After Combined Forms

Form	Mutation	Example
sa / san	lenition	sa teach → sa theach (but sa before consonants only)
den	lenition	den chéad uair
don	lenition	don fhear
ón	lenition	ón siopa (ón + s does not lenite s)
leis an	eclipsis (standard)	leis an mbean
ag an	eclipsis (standard)	ag an gcapall
ar an	eclipsis (standard)	ar an mbord

"Sa" vs "San"

Before	Form	Example
Consonant (lenitable)	sa + lenition	sa bhaile (in the town)
Vowel	san	san oíche (in the night)
f + vowel	san fh...	san fharraige (in the sea)
s + vowel	sa	sa samhradh (in the summer)

Examples in Context

Irish	English	Note
sa teach	in the house	i + an → sa (but "teach" not lenited here as t- is special)
den chéad uair	for the first time	de + an → den + lenition
leis an mbean	with the woman	le + an → leis an + eclipsis
ón siopa	from the shop	ó + an → ón
ag an gcapall	at the horse	ag + an + eclipsis
ar an mbord	on the table	ar + an + eclipsis
don fhear	for the man	do + an → don + lenition
faoin tuath	in the countryside	faoi + an → faoin
sa bhaile	at home / in the town	sa + lenition
tríd an bhfuinneog	through the window	trí + an → tríd an + eclipsis

Common Mistakes

Separating preposition and article

• Wrong: i an teach
• Right: sa teach
• Why: Most prepositions merge with the article into a combined form. You cannot leave them as separate words.

Applying the wrong mutation

• Wrong: leis an bhean (lenition)
• Right: leis an mbean (eclipsis)
• Why: In the standard language, leis an, ag an, and ar an cause eclipsis, not lenition. (Note: some dialects do use lenition here.)

Forgetting that "sa" causes lenition

• Wrong: sa baile
• Right: sa bhaile
• Why: The form sa triggers lenition on the following noun.

Practice Tips

1. Take ten common nouns and practice combining them with sa, leis an, ar an, and ón. Pay attention to which mutation each requires.
2. Describe the location of objects in a room using preposition + article combinations: ar an mbord (on the table), sa chathaoir (in the chair), ag an doras (at the door).

Related Concepts

• Simple Prepositions — the basic prepositions before they combine with the article