xx.
Outlines of Gaelic etymology.
leading I. E. series of vowel gradations are six in number, as follows:—
| Normal. | Deflected. | Weak. | |
| 1. e-series | e | o | nil |
| but | ei | oi | i |
| 2. ē-series | ē | ō | ɘ |
| 3. ā-series | ā | ō | ɘ |
| 4. ō-series | ō | ō | ɘ |
| 5. a-series | a | ā | (a) |
| 6. o-series | o | ō | o |
Corresponding to the e, o, nil series are the two “strong” vowel grades ē, o, as in sed, sit, sod, sēd, sōd, si‑zd, found in Latin sedeo (sed), G. suidhe (sod), G. sìth [properly sìdh], peace (sēd), Eng. soot (sōd), Lat. sīdo (si‑zd).
The e-series in full is as follows:—
| Normal. | Deflected. | Weak. | |
| e simple | e | o | nil |
| ei | ei | oi | i |
| eu | eu | ou | u |
| er (or el, en, em) | er | or | ṛ |
To all these correspond "reduced" long forms—to ei belongs to ī, to eu belongs ū, and to the consonant-vowels correspond the long ṝ, ḹ, ṇ̄, ṃ̄. We may also here add the triple ve, vo, u (vet, vot, ut, as in G. feitheamh, ùine, uiridh; vel, vol, ul as in falt, O. Ir., Mod. Ir. folt, olann).
Some Gaelic examples will now be given.
(1) The e-series. G. eadh, uidhe from *pedo‑, *podio-; tigh, tugha, from *tegos, *togio‑; geas, guidhe from ged, god; cleachd, cleas, cluich, etc. In ei we have the complete set meit, moit, mit in mèith, maoth, meata or miosa; further cliathach, claon from klei, kloi; fianuis, fios from veid, vid; gaoth, geamhradh from ghoi, ghi; and others. The diphthongs eu, ou cannot be differentiated, but the short form of the root occurs, as in ruadh, roduidh from roud, rudd; buail, buille from bhoud, bhud; cluas, cluinn from kleu, klu; nuadh, nodha (?) The liquids show the changes also: beir, breith from ber, bṛ, and in the sense of speech we have also bràth, judgment (bṝtu‑). The root pel is especially rich in forms: iol (*pelu‑), uile (*polio‑), lìon (*plēno‑, Lat. plēnus, from plē), làn (either *plōno, plō, Eng. flood, or *pḹ-no‑, from pḹ‑), that is, root forms pel, pol, pḷ, plē, plō, pḹ, meaning “full.” In n we have teann, tana (*tendo- tṇnavo‑, according to Brugmann), and teud; from gen we get the long forms gnē in gnìomh and gnō in gnàth. In nem we have nèamh, heaven, O. Ir. nem, and nàmhaid, foe, from nōm (Gr. νωμάω).
