v. The combination iwy has four sounds: (1) the mixed triphthong i̯w͡y, as in neithi̯w͡yr, § 34 ii. It occurs in verbal forms when the terminations ‑w͡yf, ‑w͡yd, ‑w͡ys are added to stems in i̯, § 35; as rhodi̯w͡yf ‘I may walk’, tybi̯w͡yd ‘it was thought’.
(2) ī́w͡y disyllabic. It occurs when the above endings are added to stems in vocalic i, as gweddī́w͡yf (3 syll., see example in § 201 ii (2)); and in compounds of di- with stems having w͡y, as in di-w͡yr ‘not bent’ (gŵyr ‘bent’).
(3) iw̯ɥ or (4) iw̯ỿ according to position, as in lliw̯ɥdd g. 164 ‘painter’, pl. lliw̯ỿddi̯on; diw̯ɥd ‘diligent’ spv. diw̯ỿtaf. These sounds may occur either when iw̯ is followed by ɥ or ỿ or when i is followed by w̯ɥ or w̯ỿ in word-formation.
§ 38. i. The distinction between the falling diphthong w͡y and the rising diphthong w̯ɥ, both written wy, is an important one. The difference between them is seen most clearly in monosyllables such as gŵɥr ‘he knows’, gw̯ɥ̂r ‘men’. In other positions they are liable to be confused in the dialects, and in a few cases we find confusion even in lit. W.
In ordinary written W. the falling diphthong when long is denoted by ŵy (only used initially and after g, ch), but when short or unaccented there is no method in ordinary use by which it can be distinguished; in that case it is printed w͡y, where necessary, in this book. The rising diphthong is indicated by marking the w̯ a consonant.
ii. In monosyllables wy represents the falling diphthong except when preceded by g or ch; thus dŵɥn ‘to bring’, brŵɥn ‘rushes’, cŵɥn ‘complaint’, clŵɥd ‘hurdle’, llw͡ybr ‘path’, hŵɥnt ‘they, them’, cw͡ymp ‘fall’. Words beginning with g or ch have usually the rising diphthong, as gw̯ɥn ‘white’, gw̯ɥrdd ‘green’, gw̯ŷdd ‘trees’, chw̯ɥrn ‘roaring’, chw̯ŷth ‘blows’; the exceptions are Gŵɥ ‘the Wye’, gŵɥdd ‘goose’, gŵɥdd ‘presence’, gŵɥl ‘vigil, holiday’, gŵɥl ‘modest’, gŵɥll ‘goblin’, gŵɥr ‘knows’, ''gŵɥr ‘a bend’, gw͡ystl ‘pledge’, gŵɥth ‘anger’, chŵɥdd ‘swelling’.
Note the following words which conform to the rule, though spelt like some of the above-mentioned exceptions: gw̯ŷdd ‘trees’, gw̯ŷl ‘sees’ § 173 iv (1), gw̯ɥll ‘darkness’.
iii. When a word has the falling diphthong ŵɥ in its simple form, the diphthong remains so in all derivatives; thus mŵɥn
