2. In anaphoric reference to a singular noun or pronoun of undetermined gender: he or she.
Especially in relation to a noun phrase involving one of the indefinite determiners or pronouns any, each, every, no, some, anybody, anyone, etc.

This use has sometimes been considered erroneous.

a1375   William of Palerne (1867) l. 2179   Hastely hiȝed eche wiȝt..til þei neyȝþed so neiȝh..þere william & his worþi lef were liand i-fere.
c1450  (▸?c1400)    Three Kings Cologne (Cambr. Ee.4.32) 6   Noman was hardy in all þat countrey to sette aȝens hem, for drede þat þey hadde of hem.
1526   W. Bonde Pylgrimage of Perfection iii. sig. IIIiiiiv,   If..a psalme scape any person, or a lesson, or els yt they omyt one verse or twayne.
a1535   J. Fisher Wayes to Perfect Relig. in Eng. Wks. (1876) i. 383   He neuer forsaketh any creature vnlesse they before haue forsaken them selues.
1681   London Gaz. mdclxii. 4   If any Person desire to be furnished with young Abeele Plants..they may be furnished with what quantity they please,..at 10s. a hundred.
1698   A. Boyer & J. Savage tr. P. Le Lorrain de Vallemont in T. Hearne Ductor Historicus I. ii. iv. 130   Leaving every Body to their liberty of believing what they pleas'd.
1749   H. Fielding Tom Jones III. viii. xi. 251   Every Body fell a laughing, as how could they help it.
1759   Ld. Chesterfield Let. 27 Apr. (1932) (modernized text) V. 2350   If a person is born of a..gloomy temper..they cannot help it.
1835   W. Whewell in J. M. Douglas Life & Corr. W. Whewell (1881) 173   Nobody can deprive us of the Church, if they would.
1858   W. Bagehot in National Rev. Oct. 476   Nobody fancies for a moment that they are reading about any thing beyond the pale of ordinary propriety.
1866   J. Ruskin Crown Wild Olive (1873) §38. 44   Now, nobody does anything well that they cannot help doing.
1874   G. W. Dasent Half a Life 3   Every one likes to keep it to themselves as long as they can.
1932   L. Hughes Let. 16 May in L. Hughes & C. Van Vechten Remember me to Harlem (2001) 95   Nobody can bother you until they've passed three butlers, two secretaries, and my personal assistant!
1968   Listener 3 Oct. 440/3   When somebody becomes prime minister they're immediately put on a pedestal.
1998   A. Pease & B. Pease Why Men don't listen & Women can't read Maps (1999) viii. 212   The psychiatric label for a transgender person is that they are suffering Gender Identity Disorder.