idir

• eidir

From Old Irish eter, from Proto-Indo-European *h₁enter (“between”). Cognate with Latin inter (“between”) and Sanskrit अन्तर् (antár, “between, within, into”). Compare Scottish Gaelic eadar.

• IPA^(key): /ˈɪdʲəɾʲ/
• (Cois Fharraige) IPA^(key): /ˈɛdʲəɾʲ/ (also spelled eidir)
• (Ulster) IPA^(key): /ˈɛd̪ˠəɾʲ/[1]

idir (plus nominative in singular, dative in plural, triggers lenition except in certain constructions with distance, time, difference, or opposition)

1. between

   idir fhir agus mhná ― between men and women

   • 2014, Bruno Coulais (lyrics and music), “Amhrán Na Farraige [Song of the Sea]”:

     Idir ann is idir as. Idir thuaidh is idir theas.

     Between in and between out. Between north and between south.

2. both (paired with agus (“and”))

   idir chait agus mhadraí ― both cats and dogs

3. partly...partly..., half...half... (paired with agus (“and”))

   idir bheith ag caint agus chanadh ― half talking, half singing

• In modern usage, only has inflected forms in the plural. Is used with nouns and singular pronouns in combination with another noun or pronoun:

idir é agus mé ― between him and me

• In the sense of strictly "between", does not trigger lenition when a definite path can be traced between the things being described; often occurs with distance, time, and difference and almost always occurs with opposition:

idir Maigh Eo agus Gaillimh ― between Mayo and Galway

idir fómhar agus geimhreadh ― between autumn and winter

an difríocht idir maith agus olc ― the difference between good and evil

cogadh idir tíortha ― war between countries

cluiche idir Baile Átha Cliath agus Corcaigh ― a game between Dublin and Cork

But:

idir thithe ― between houses (indistinct, cannot be represented by a definite path)

idir shaoirí ― between holidays

cur idir dhaoine ― to interfere between people

• When mutation does occur, the s in agus blocks mutation of d, s, and t in the following word even though it is not the trigger:

idir Phádraig agus Tadhg ― between Patrick and Tadhg

idir rith agus siúl ― half running, half walking

idir shonas agus deora ― between happiness and tears

From Old Irish etir (“at all”), originally 3rd person sg. neut. form of Old Irish eter (“between”).

• IPA^(key): /ˈitʲɪɾʲ/

idir

1. at all

   Chan eil idir. ― Not at all.

   Chan e idir. ― That is not it at all.

   Cha tig e idir. ― He will not come at all.

   No idir air a bhruicheadh. ― Nor even boiled.

   Chan eil e gu math idir. ― He is not at all well.

   Cha deanainn idir e. ― I would not do it on any account.

   Cha toil leam purpaidh idir. ― I don't like purple at all.

2. yet

• Edward Dwelly (1911), “idir”, in Faclair Gàidhlig gu Beurla le Dealbhan [The Illustrated Gaelic–English Dictionary], 10th edition, Edinburgh: Birlinn Limited, →ISBN
• G. Toner, M. Ní Mhaonaigh, S. Arbuthnot, D. Wodtko, M.-L. Theuerkauf, editors (2019), “etir”, in eDIL: Electronic Dictionary of the Irish Language
• A Pronouncing and Etymological Dictionary of the Gaelic Language (John Grant, Edinburgh, 1925, Compiled by Malcolm MacLennan)