reithid

Old Irish

reithid (conjunct ·reith, verbal noun riuth or rith)

to run, to speed
- c. 750-800 Torche na nDessi from Laud 610, published in "The Expulsion of the Déssi", Ériu 3 (1907), edited by Kuno Meyer, pp. 135-142, line 207
  Amal ossa, is [s]amlaid ro·ráthatar ass.
  They ran away like deer.
  (literally, “Like deer, it's like them they ran away.”)

Simple, class B I present, á preterite, unreduplicated s future, s subjunctive
		1st sg	2nd sg	3rd sg	1st pl	2nd pl	3rd pl
present indicative	abs.	rithu, rithim	rithi	rethid, rethith	rethmai	reithe	rethait
	conj.	·riuth	·rethi	·reith	·retham	·reithid	·rethat
	rel.			rethes, rethess			retae, rethae

imperfect indicative							·reitis, ·reithis

preterite	abs.			ráith			ráthatar
	conj.
	rel.

perfect	deut.						ro·ráthatar
perfect	prot.						·rorthatar, ·rorthetar, ·rrúairthetar

future	abs.			reiss
	conj.			·ré			·ressat
	rel.

conditional

present subjunctive	abs.			reiss
	conj.			·ré			·ressat
	rel.

past subjunctive				·ressed

imperative

verbal noun		rith, riuth
past participle
verbal of necessity

In all modern Goidelic languages, the verbal reflex of reithid came to adopt the same vowel as the verbal noun riuth.

Mutation of *reithid*
radical	lenition	nasalization
reithid also rreithid after a proclitic ending in a vowel	reithid pronounced with /r(ʲ)-/	unchanged

Note: Certain mutated forms of some words can never occur in Old Irish.
All possible mutated forms are displayed for convenience.

Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “reithid”, in eDIL: Electronic Dictionary of the Irish Language
Pedersen, Holger (1913) Vergleichende Grammatik der keltischen Sprachen [Comparative Grammar of the Celtic Languages] (in German), volume II, Göttingen: Vandenhoeck und Ruprecht, →ISBN, § 597, pages 597–598