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Dual number in Irish (Déach): Meaning, Pronunciation, Usage

‘déach’ also means: dual

The Irish for dual number is déach, a masculine noun (plural déacha).
Updated October 2026Report a mistake

How to say “dual number” in Irish

Irish:
déach
English:
dual number
Word type:
noun
Gender:
masculine, first declension
Pronunciation:
“jayokh”  /dʲeːx/
Various forms
Plural:
déacha (dual numbers)
Genitive singular:
déigh, an déigh (e.g. úsáid an déigh, the use of the dual)
Genitive plural:
déacha, na ndéacha (e.g. foirmeacha na ndéacha, the forms of the duals)

What does “déach” mean?

dual number
In grammar, the dual is the number category used for exactly two things, as in Irish after 'dhá', where the noun takes a special form.Also: dual form, grammatical dual.
Other entries for “déach”

The same spelling has its own page as:

“Déach” with the article

The plural of dual number in Irish is déacha. Here is déach after the article (an t-alt), in the singular and the plural.

an déach
the dual number
No change after an
na déacha
the dual numbers
Plural: no change after na

“Déach” in a sentence: Irish examples

Common Irish sentences using déach, the Irish word for dual number.

Úsáidtear an déach i ndiaidh 'dhá'.
The dual is used after 'dhá'.
Tá déach fós sa Ghaeilge.
Irish still has a dual.
Mhínigh an múinteoir rialacha an déigh dúinn.
The teacher explained the rules of the dual to us.
Bhí déacha ag an tSean-Ghaeilge.
Old Irish had dual forms.
Is iarsma den déach é 'dhá chos'.
'Dhá chos' is a remnant of the dual.
Ní thuigim an déach i gceart fós.
I don't understand the dual properly yet.
Tá caibidil ar an déach sa leabhar gramadaí.
There is a chapter on the dual in the grammar book.

Other nouns in Irish

More everyday Irish nouns to learn next.

Dual number in Irish: frequently asked questions

What is the Irish for dual number?

The Irish for dual number is déach (pronounced “jayokh”). It’s a masculine noun and the plural is déacha.

How do you pronounce déach in Irish?

Déach is said like “jayokh” (IPA /dʲeːx/).

What is the plural of dual number in Irish?

The plural of déach is déacha; with the article, na déacha means “the dual numbers”. The genitive plural is déacha, as in foirmeacha na ndéacha (the forms of the duals).

Does déach have more than one meaning?

Déach also has its own entry as an adjective meaning dual.

Why does déach change to dhéach or ndéach?

Irish changes the start of some words after certain words. After mo (my) déach becomes mo dhéach (lenition), and after ár (our) or i (in) it becomes ár ndéach (eclipsis).

Where does a learner meet the dual in modern Irish?

Mainly after 'dhá', where a feminine noun can keep a special form, for example 'dhá láimh' beside 'lámh'. Grammarians call this the 'déach'.

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