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Substitution in Irish (Ionadú): Meaning, Pronunciation, Usage

‘ionadú’ also means: substitute teaching · placement

The Irish for substitution is ionadú, a masculine noun (plural ionaduithe). Ag ionadú is representing, from the verb ionadaigh.
Updated October 2026Report a mistake

How to say “substitution” in Irish

Irish:
ionadú
English:
substitution, substitute teaching, placement
Word type:
noun (verbal noun)
Verbal noun of:
ionadaigh, to represent (ag ionadú, representing)
Gender:
masculine
Pronunciation:
“UN-uh-doo”  /ˈʊnˠəd̪ˠuː/
Various forms
Plural:
ionaduithe (substitutions)
Genitive singular:
ionadaithe, an ionadaithe (e.g. modh an ionadaithe, the method of substitution)
Genitive plural:
ionaduithe, na n-ionaduithe (e.g. uimhir na n-ionaduithe, the number of substitutions)

What does “ionadú” mean?

“Ionadú” has three alternative meanings. The most common comes first.

substitution
The act of putting one person or thing in place of another; the verbal noun of the verb ionadaigh.Also: replacement, substituting, replacing.
2 other meanings: substitute teaching or placement
2substitute teaching
Working as a substitute, especially filling in for an absent teacher.Also: subbing, covering, standing in.
3placement
The act of placing or positioning something or someone.Also: placing, positioning.

“Ionadú” as a verbal noun

After ag, ionadú means representing: it is the verbal noun of the verb ionadaigh (to represent). A noun that follows it goes into the genitive.

agat
+
ionadúverbal noun
=
ag ionadúrepresenting

“Ionadú” with the article

The plural of substitution in Irish is ionaduithe. Here is ionadú after the article (an t-alt), in the singular and the plural.

an t-ionadú
the substitution
Masculine nouns take t before a vowel after an
na hionaduithe
the substitutions
Plural: na adds h before a vowel

“Ionadú” in a sentence: Irish examples

Common Irish sentences using ionadú, the Irish word for substitution.

Rinne sé ionadú sa scoil an tseachtain seo caite.
He did substitute teaching in the school last week.
Tá an t-ionadú ag dul go maith di.
The subbing is going well for her.
Is post ionadaithe atá agam faoi láthair.
I have a substitute job at the moment.
Rinne an bainisteoir trí ionadú sa dara leath.
The manager made three substitutions in the second half.
Bhí ionaduithe déanta ar na páirteanna briste.
The broken parts had been replaced.
Úsáidtear ionadú i gceisteanna matamaitice go minic.
Substitution is often used in maths questions.
Ba é mo chéad lá ionadaithe é inniu.
Today was my first day subbing.

Other nouns in Irish

More everyday Irish nouns to learn next.

Substitution in Irish: frequently asked questions

What is the Irish for substitution?

The Irish for substitution is ionadú (pronounced “UN-uh-doo”). It’s a masculine noun and the plural is ionaduithe. Depending on context it can also mean substitute teaching or placement.

How do you pronounce ionadú in Irish?

Ionadú is said like “UN-uh-doo” (IPA /ˈʊnˠəd̪ˠuː/).

What is the plural of substitution in Irish?

The plural of ionadú is ionaduithe; with the article, na hionaduithe means “the substitutions”. The genitive plural is ionaduithe, as in uimhir na n-ionaduithe (the number of substitutions).

Does ionadú have more than one meaning?

Yes. Ionadú can mean substitution, substitute teaching or placement, depending on context; the first is the most common.

Why does ionadú sometimes have a t or h in front of it?

Irish nouns beginning with a vowel take a prefix after certain words: an t-ionadú (the substitution), a hionadú (her substitution), a n-ionadú (their substitution), na hionaduithe (the substitutions).

What is the difference between ionadú and ionadaíocht?

Ionadú is the act of substituting or subbing, the verbal noun of ionadaigh, while ionadaíocht usually means representation or deputising, as in ionadaíocht pholaitiúil.

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