Definition of "constancy"

A little water clears us of this deed:How easy is it, then! Your constancyHath left you unattended.

c. 1606 (date written), William Shakespeare, “The Tragedie of Macbeth”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act II, scene ii]

Punctuality is a species of Constancy, a very unfashionable quality in a Lady.

1777, Richard Brinsley Sheridan, The School for Scandal, IV.iii

And, I do not know that I should be fond of preaching often; now and then, perhaps, once or twice in the spring, after being anxiously expected for half a dozen Sundays together; but not for a constancy; it would not do for a constancy.

1814 July, [Jane Austen], chapter III, in Mansfield Park: […], volume III, London: […] T[homas] Egerton, […], page 68

Constancy of character is what is chiefly valued and sought for by naturalists.

1871, Charles Darwin, “7, "On the Races of Man,"”, in The Descent of Man, and Selection in Relation to Sex. […], volumes (please specify |volume=I or II), London: John Murray, […]

The overall retention rate of 68 per cent indicates a robust constancy of the linguistic features investigated.

2014, James Lambert, “Diachronic stability in Indian English lexis”, in World Englishes, page 124

younger spirits […] whose constanciesExpire before their fashions.

c. 1604–1605 (date written), William Shakespeare, “All’s Well, that Ends Well”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene ii]