§ 8. Accent.
In Gaelic, only the stress accent exists, and it is placed always on the first syllable. The accent of the Old Gaelic was likewise on the first syllable, save in the case of the verb. Here in the compounded verbs the stress accent rested on, as a rule, the second syllable; but the imperative placed the accent on the first syllable, and this also took place after the negative and interrogative particles and after the conjunctions gu’n and na’n (da’n). Thus faic, see thou, is for f‑aid‑c, with accent on the preposition ad, for it is imperative; the future chì stands for the old present at-chí, videt, where the accent is on the root cí. Again in cha’n fhaca the negative brings the accent on the prefix ad, that is, f‑ad-ca. When the accent is on the prefix, its ending consonant and the initial consonant of the root coalesce and result in a preserved G. intervocalic consonant, but the root suffers truncation: when the accent is on the root, these consonants are aspirated, and the root is preserved. The ten irregular verbs in G. present sufficient illustrations of this rule. The preposition con, when accented, was always con, when unaccented it was com (comh). In the unaccented syllables, long vowels become short (àireamh from *ád-rîm, anail for O. Ir. anál), and in many cases change completely their grade, as from small to broad (e.g. còmhnadh, O. Ir. congnam, from gnìomh, and the compounds in ‑radh and ‑lach).
II. Word-building.
Word-building consists of two parts—composition and derivation. The first deals with the compounding of separate words; the second deals with the suffixes (and prefixes) that make up the stem of a word from its root.
(1) The compound may be two stems welded together: righ-theach, palace, *rîgo-tegos, “king’s house”; righ-fhàidh, royal prophet—“king who is a prophet”; ceann-fhionn, white-headed, penno-vindo‑s; ceithir-chasach, four-footed; dubh-ghlas, dark-blue; crannchur, lot, “casting the lot.” These are the six leading relationships brought out in compounds. In Celtic the first stem is nearly always in o‑, as Teuto-bōdiaci, G. sean-mhathair (but Catu-slôgi, Mori-dûnum, G. Muirgheal). Consider the following compounds: iodhlann, mìolchu, òircheard, buarach, cèardach, clogad, bàthach, eilthire, gnàth-fhocal, moirear, leth-chas, leth-trom, etc.
The following are common prefixes: ath‑, re‑, ath-ghlac, re-capture; ban‑, she, ban-altrum, bantrach; bith‑, ever‑, bith-bheò, bith-bhuan; il‑, iol‑, many; ion‑, fit; sìr‑, sìor‑, ever‑, fìr‑, fìor‑, very, saobh‑, pseudo‑.