From the second edition (1989):
(ˈhæpɪnɪs) [f. as prec. + -ness.]

The quality or condition of being happy.

1. Good fortune or luck in life or in a particular affair; success, prosperity.

1530 Palsgr. 229/1 Happynesse, prosperité. 1591 Shakes. Two Gent. i. i. 14 Wish me partaker in thy happinesse, When thou do'st meet good hap. 1614 Raleigh Hist. World II. v. i. §i. 263 This also‥was a part of her happinesse; that she was neuer ouer-laied with too great warres at once. a1704 T. Brown Sat. of Antients Wks. 1730 I. 24 Whether‥we follow them by the only force of natural happiness, or instinct. 1705 W. Bosman Guinea 277 It is a very great Happiness, and particular Providence of God, that the Sea and Rivers here seem‥to contest. Mod. When in Switzerland I had the happiness to meet a friend whom I had not seen for many years.

b. in pl.

1601 R. Johnson Kingd. & Commw. (1603) 36 Nature hath‥heaped into this teritorie‥all those delightful happinesses. 1678 Otway Friendship in F. 18 Ten thousand happinesses wait on you. 1739 Cibber Apol. (1756) I. 69 It was therefore one of our greatest happinesses. 1885 Spurgeon Treas. Dav. Ps. cxxviii. 2 Heaped up happinesses in the plural belong to that man who fears the Lord.

2. The state of pleasurable content of mind, which results from success or the attainment of what is considered good.

1591 Spenser Ruines of Time 357 Like beast [that] hath no hope of happinesse or blis. 1611 Shakes. Cymb. v. v. 26 To sowre your happinesse, I must report The Queene is dead. 1667 Milton P.L. viii. 621 Let it suffice thee that thou know'st Us happie, and without Love no happiness. 1725 Watts Logic ii. v. §3 Happiness consists in the attainment of the highest and most lasting natural good. 1734 Pope Ess. Man iv. 1 Oh Happiness! our being's end and aim! Good, Pleasure, Ease, Content! whate'er thy name. 1851 H. Spencer Soc. Stat. Introd. 5 Happiness signifies a gratified state of all the faculties. 1868 Bain Ment. & Mor. Sc. iii. i. §8 Each one's happiness may be defined as the surplus gained when the total of pain is subtracted from the total of pleasure.

b. greatest happiness of the greatest number, as a principle of moral and political action: first enunciated by Hutcheson 1725, thence taken into Italian ‘la massima felicità nel maggior numero’ by Beccaria Dei Delitti e delle Pene (Monaco, 1764) 4 (English translation 1766); thence in Priestly 1768, and Bentham 1776; at the instance of Gen. P. Thompson, 1829, shortened to ‘greatest happiness principle’, ‘rule of greatest happiness’.

1725 Hutcheson Ideas Beauty & Virtue iii. § 8. 164 That Action is best which accomplishes [1726 procures] the greatest Happiness for the greatest Numbers; and that worst, which in like manner occasions Misery. 1768 Priestley Ess. on Govt. 1776 Bentham Fragm. on Govt. Wks. 1843 X. 142. 1829 Gen. P. Thompson Exerc. (1842) I. 130 The latest improvement, therefore, of the philosopher [Bentham]‥is to dismiss the superfluous ‘greatest number’, and declare that the just object of politics and morals, is simply ‘the greatest happiness’‥And the accessary proposition is, that the greatest aggregate of happiness must always include the happiness of the greatest number. Ibid. 240 The rule of the greatest happiness evidently includes the motive. 1834 Ibid. III. 118 But these [ascetics] too, were pursuers of the Greatest-Happiness Principle‥after a sort. 1894 B. Kidd Soc. Evolut. x. (1895) 290 ‘The greatest happiness of the greatest number—long a prominent doctrine in English politics.

3. Successful or felicitous aptitude, fitness, suitability, or appropriateness; felicity.

1599 Shakes. Much Ado ii. iii. 191, Clau. He is a very proper man. Princ. He hath indeed a good outward happines. 1602 —— Ham. ii. ii. 213 How pregnant (sometimes) his Replies are? A happinesse That often Madnesse hits on. 1635 N. R. Camden's Hist. Eliz. iii. 361 The charge of the whole fleet she committed to Charles Howard of Effingham‥of whose happinesse she had a very good persuasion. a1668 Denham in Guardian No. 164 ⁋3 There being certain graces and happinesses peculiar to every language. 1779–81 Johnson L.P., Cowley Wks. II. 23 He‥reduces it from strength of thought to happiness of language. 1826 Disraeli Viv. Grey iv. i, Possessing no vigour of language, and gifted with no happiness of expression.