DSL - SND1 O, letter of the alphabet . The fifteenth letter of the alphabet , pronounced [o:] (Sc. 1761 Magopico (1810) 1; Bnff. 1836 in Ellis E.E.P. V. 777, 1893 G. G. Green Kidnappers ii.; Ork. 1920 J. Firth Reminisc. 133; Sh. 1943 P. Jamieson Letters 248).
1. In Sc. it represents the mid back tense rounded sound [o], slightly more fronted and raised than the Eng. equivalent, and the mid back lax rounded sound , the former not being diphthongised to [ou] as in Eng.  not normal in m. and s.Sc. occurring gen. in attempts to reproduce Eng. pronunciation in words like boat, coal, force, four, note, post, road, story, sword, worn. Cf. P.L.D. §§ 52, 53. This sound was noted by phoneticians in the 18th c., e.g. J. Elphinston Propriety (1787) II. 9, and is sometimes indicated by a phonetic spelling, e.g. rod (road), odd (ode) (s.Sc. 1825 Lockhart Scott lxi., Wilson Noctes Amb. (1855) I. 74). In I.Sc. and Mry. Firth coastal areas, however,  is the reg. sound in such cases. See P.L.D. §§ 52, 129, 164, 168. These sounds are lengthened when final and accented, and before voiced fricatives and r. See P.L.D. § 29. In unaccented syllables o is reduced to [ or I, ]. See [E], 1. (2) (b). In some dialects dog is sounded [dg] and [MONIE] as [mne]. Cf. also [BODY], [RUB], v.2 In [SCHO] (she), an archaic spelling surviving into the 18th c., o represents [ø]. See s.v. o, representing O.Sc. Q, as in body, bonnie, coat, folk, fore, frozen, horn, nose, story, etc., etc., was formerly sounded as [, occas. u] in s.Sc. but this is now obs. or nearly so. See Murray D.S.C.S. 111, 147, Watson W.-B. § 71 and P.L.D. § 105.
2. o is conjoined: (1) with i or y to form the diphthong [I, oe] though this is rare in Sc. See P.L.D. § 46. As in Eng. this diphthong came to be pronounced [i] in the 16th c. and this has remained in Sc. when the sound returned to [i] in Eng. in the 18th c. Cf. the spellings
[BILE], v., jine ( [JOIN]), pint ( [POINT]). When final, as in boy, joy, ploy, toy [i] is now heard, though boy seems to have been pronounced rather like [bui] in the 18th c. (Sc. 1764 Scots Mag. (April) 187) and joy as [de] (Sc. 1788 Burns Letters (Ferguson) No. 170). See P.L.D. § 46 (2). This sound (i) is also heard as a local development of [i, e] from O.E., O.N., O.Fr. i. Cf. oy (I), foive (five), moy (my) (Sc. 1779 A. Scott The Contrast 7), doyk (dike) (Bch. coast 1804 Sc. N. & Q. (Oct. 1928) 193), I, 3. and P.L.D. §§ 131, 148, 157 (2); (ii) interchanges sporadically with o before t, see [DOITER], goit ( [GOTE]), [KNOIT], [STOIT] ( [STOT]), toit ( [TOTE]); (2) with u or w to form the diphthong [u] ([u] in Ork.), as in P.L.D. § 164.8, written ou or ow deriving from various sources (see P.L.D. § 47): (i) O.E. -ow-, e.g. [FOWER], [GROW], [YOWE]. See P.L.D. § 35.5.; (ii) O.N. -au-, e.g. [COUP], v.2, [GOWPEN], [LOWP], [NOWT], [ROUP], [ROWAN]; (iii) O.E. -o-, -oh-, O.N. -og-, e.g. [BOW], n.4, v.3, [LOW], n., [LOWN], adj., [OWSEN], [TROW]; (iv) rarely from O.Fr. -ou- as in How, n.1; (v) from o before labials as in [DOUP], [DOWF], [HOWF], [HOWP], [SOWP]; and g in Cai., Rs., Fif., as in [BOWG], [DOWG], [FOWG]; before -ld in Cai. and Arg., bowld, cowld. See P.L.D. § 149; (vi) by vocalisation: of l in the collocation -ol cons. Hence bow ( [BOLL]), [BOWT], [COW], v.1, [FOWK], [GOWD], [HOW], adj., [KNOW], [ROW], [SOWTHER]. See [L], 1. and P.L.D. §§ 55, 78.2.; or v intervocalically as in [COWER], v., [OWER]; (vii) this diphthong also develops (a) in ne.Sc. from O.E. -aw as in fyow ( [FEW]), dyow ( [DEW]), nyow ( [NEW]); and in Romance words like beauty, duty, pewter. See P.L.D. § 130.1; (b) in Fif., obsol., from -oi- as in [BOWL], v.1, (boil), [DOWTIT], jown ( [JOIN]), pount (point), vouce (voice). See Fif. 1795 Stat. Acc.1 IX. 297, XV. 265; (c) in s.Sc. from O.E., O.N. , l, O.Fr. ou final, as in allow, cow, dow ( [DOO]), fow ( [FU]), now ( [NOO]), pow ( [PU]), yow ( [YOU]); and from O.E. -oh-, -uh- + t as in bow(ch)t (buy), [DOWTER], houch ( [HOCH], n.), now(ch)t ( [NOCHT]), sow(ch)t ( [SEEK]). See P.L.D. §§ 101, 111.
3. o appears also in various digraphs: (1) oa, used as in Eng. to represent a long o sound [o:] as in 1., e.g. in the phonetic spellings boax, coarn, Goad, joab, noat; (2) oe, (i) = [o:] as in Eng., e.g.
[HOE], joe (Jo, n.1), [SOE]; (ii) = [ø:, y:] rare and obs., usu. in informal writing of the 18th c., e.g. goed ( [GUID]), loe ( [LUVE]), poer ( [PUIR]). Cf. also Ayr. 1811 W. Aiton Agric. Ayr. 688; (3) oo, (i) = [u], alternating with ou, ow (obs.), u, as in [COO], [DOON], foo ( [FU]), [GOO], hoot ( [HOUT]), joodge, joog ( [JOUG]), [LOOM], n.2, [NOO], poo ( [PU]), [SHOOT] (suit), toor ( [TOUR]). This is phs. the commonest representation of this sound in the later 19th c. See P.L.D. § 20 and (4) (i); (ii) alternating with ui, eu (Ork.), o-e (obs.), u-e, to represent [ø, y > I] from O.E., O.N. , O.Fr. u. See P.L.D. §§ 20, 35. This is a 16th c. adaptation of the Eng. spelling for the equivalent Eng. sound [u] developed from the same sources and given currency in the 18th c. esp. by Ramsay. Cf. Ramsay Ever Green (1724) I. 2 note. The quality of the vowel so spelt can be freq. established by the rhymes, e.g. whid: red-wood (Sc. 1719 Ramsay Poems (S.T.S.) I. 125), as well as on philological grounds, e.g. [DOOL], n.1, [FOOM], shool, shoon, toom; (4) ou, (i) = [u], as in [BOUK], [CROUSE], [DOUCE], doun ( [DOON)], [DOUR], fou ( [FU]), [FLOUR], [JOUK], [LOUN], [STOUR], [TOUN]. This spelling is gen. preferred in this dictionary, hence [HOUR], [HOUSE], [LOUD], [MOUSE], [MOUTH], [POUCH], [SOUR] [ur, hus, lud, mus, mu, put, sur], etc. See (3) (i); (ii) = [u], as in [COUP], v.1, v.2, [DOUP], goud ( [GOWD]), houk ( [HOWK]), houp ( [HOWP]), loup ( [LOWP]), soup ( [SOWP]), rout ( [ROWT]), stoup ( [STOWP]). The ow spelling is preferred in this dictionary to distinguish from (i); (5) ow, (i) = [u], e.g. dow ( [DOO]), drowth ( [DROUTH]), fow ( [FOU]), lown ( [LOUN]), plow ( [PLOO]), sowk ( [SOUK]), sowr ( [SOUR]). This phonetic value for ow became rare before 1750. The spelling ow also appears in such words as bow, brown, drown, how, now, etc., esp. in the 18th c., though [u] is intended, partly though influence of St. Eng., partly phs. as a survival from Mid.Sc. where u and w were not clearly distinguished in MSS. In the course of the 19th c. oo came to be used chiefly for this sound, as a borrowing from St. Eng. orthography, though found as early as the 17th c. in Sc. Cf. (3) (i); (ii) = [u] as in [BOW], [COW], v., [GLOWER], [GOWD], [HOWF], [KNOW], [OWSEN], [POWNIE], [YOWL], etc. Cf. (3) (i), (4) (ii), and 2. (2).
4. o appears irreg. chiefly before a nasal for a in
[MONIE], [ONIE]; sod ( [SAD]); sone ( [SAND]), see P.L.D. § 133; wob ( [WAB]), see P.L.D. § 27.1; and for u in [ON-], pref.2