facultativeadj.

1822 Ann. Reg. 1820 (Otridge ed.) ii. App. to Chron. 718/1 In forming these quotas, neither the facultative departmental centimes, nor the communal centimes shall be taken into account.

1839 W. O. Manning Law Nations (1875) v. vii. 387 Creating what is called ‘occasional’, ‘accidental’ or ‘facultative’ contraband.

1861 M. Arnold Pop. Educ. France 50 What was..to use a French expression, facultative to the communes, what..they did or not as they liked.

1881 Times 1 July 9/6 The great schools..treat classics as obligatory, and science as merely facultative.

1884 Q. Rev. Apr. 403 Permit even for the Latin clergy a facultative celibacy.

1874 G. H. Lewes Probl. Life & Mind I. 139 The Facultative Actions are those which..are..neither inevitably nor uniformly produced when the organs are stimulated, but..take sometimes one issue and sometimes another.

1875 H. Walton Pract. Treat. Dis. Eye (ed. 3) 621 The facultative [hypermetropia] is present when objects can be accurately seen at any distance.

1884 New Sydenham Soc. Lexicon Facultative hypermetropia..those cases of hypermetropia in which objects at an infinite distance can be distinctly seen both with and without convex glasses.

1887 H. E. F. Garnsey & I. B. Balfour tr. H. A. de Bary Compar. Morphol. & Biol. Fungi vii. 356 Saprophytes..which have also the power of going through their course of development wholly or in part as parasites..may be called with Van Tieghem facultative parasites.

1900 B. D. Jackson Gloss. Bot. Terms 98/1 Facultative, occasional, incidental, as opposed to obligate; ∼ Anaërobes, organisms which can exist without the presence of free oxygen or air. ∼ Symbiont, an organism which can either exist and reach maturity independently or in symbiosis with another.

1927 H. Gwynne-Vaughan & B. F. Barnes Struct. & Devel. Fungi 13 A species which is usually saprophytic but capable of parasitic existence on occasion is described as a hemi-saprophyte or facultative parasite, and a form which is usually parasitic but sometimes saprophytic as a hemi-parasite or facultative saprophyte.

1935 Discovery Jan. 27/2 The parasitic bacteria are a large and important group in which every stage of facultative and obligate parasitism can be found.

1940 Chambers's Techn. Dict. 320/2 Facultative gamete, a zoospore which can function as a gamete.

1950 J. G. Davis Dict. Dairying 13 The following table suggests terms for describing the reaction of micro-organisms to oxygen... Facultative anaerobe, Aerophilic..Facultative aerobe, Aerophobic.

1961 Encounter 16 77 The ‘facultative homosexuals’..are those men who consider themselves heterosexually ‘normal’ but engage on occasion in some form of homosexual intercourse.