Q: I assume that “equity” and “equality” are related if you go back far enough. Please write about the history of these two words. “Equity” seems to be replacing “equality” at the university where I teach.
A: Broadly speaking, both words mean the quality of being fair or equal. Their ultimate source, and that of their many relatives in English, is the Latin adjective aequus (level, even, just)—not to be confused with the noun equus (horse).
As they’re used in modern English, “equity” and “equality” may occasionally overlap, but they’re generally used in different ways—“equity” in regard to fairness, “equality” in regard to sameness.
Here are the definitions in Lexico (formerly Oxford Dictionaries Online), which are representative of those in other standard dictionaries:
“equity: The quality of being fair and impartial.” The example given: “equity of treatment.”
“equality: The state of being equal, especially in status, rights, or opportunities.” The example given: “an organization aiming to promote racial equality.”
(Lexico is an online collaboration in which Oxford University Press provides content for a website owned by the Lexico Publishing Group, owner of Dictionary.com.)
Both words entered English writing in the 14th century, “equity” around 1315 and “equality” in the late 1390s, according to the Oxford English Dictionary.
The OED, an etymological dictionary based on historical evidence, traces the two terms, along with their relative “equal” (early 1390s), to classical Latin words derived from the adjective we mentioned above, aequus.
While “equal” came directly from the Latin aequālis, “equity” and “equality” took a less direct route into English, by way of Old French.
First on the English scene was “equity,” from the Old French equité (a derivative of the Latin aequitātem).
The Middle English spellings varied widely (“equite,” “equyte,” “equitee,” and so on), but from the beginning the noun had to do with what the OED calls “the quality of being equal or fair; fairness, impartiality; even-handed dealing.”
The dictionary’s earliest known use is a reference to the divine mystery of God’s “domes [judgments] in equyte” (circa 1315, from a poem by William de Shoreham, vicar of Chart-Sutton).
In legal language, “equity” has a special sense, one believed to have existed in writing since 1591. The American Heritage Dictionary of the English Language defines it this way: “Justice achieved not simply according to the strict letter of the law but in accordance with principles of substantial justice and the unique facts of the case.”
As the OED says, this meaning of “equity” comes from the notion that a decision “in equity” was “one given in accordance with natural justice, in a case for which the law did not provide adequate remedy, or in which its operation would have been unfair.”
While “equity” had meanings related to fairness and justice, “equality” had to do with sameness or equivalency. It came into English from the Old French équalité (today it’s égalité), which in turn was a borrowing of the Latin aequālitātem (from aequālis).
The noun “equality” is generally defined, the OED says, as “the quality or condition of being equal,” and in the earliest citation it’s used in a physical sense:
“Þe see hatte equor, and haþ þat name of equalite, ‘euennesse,’ for he is euen and playne.” (“The sea hath aequor [Latin for an even, level surface], and hath that name of equality, ‘evenness,’ for it is even and plain.”)
That passage is from John Trevisa’s translation, sometime before 1398, of De Proprietatibus Rerum, an encyclopedic Latin work compiled by the medieval scholar Bartholomeus Anglicus. We’ve expanded the quotation and taken it from a different manuscript than the OED used.
Other senses of “equality” followed. In the early 1400s, the word was used to mean equal “quantity, amount, value, intensity, etc.,” Oxford says. And in the early 1500s it was used for equal “dignity, rank, or privileges with others” or “being on an equal footing.”
Toward the end of the 16th century, these usages led to a new sense of the word: “the condition of being equal in power, ability, achievement, or excellence.” The OED credits Shakespeare with the first written evidence:
“The on-set and retyre / Of both your Armies, whose equality / By our best eyes cannot be censured” (King John, probably written in the 1590s).
One of the most common meanings today emerged in the late 19th century in the phrase “equality of opportunity,” which the OED defines as “equal chance and right to seek success in one’s chosen sphere regardless of social factors such as class, race, religion, and sex.”
The dictionary’s earliest example is from an 1891 issue of the Economic Review (London): “It will possibly, however, be contended that here the ideal is equality of Opportunity.”
Today the phrases “equality of opportunity” and “equal opportunity” (first recorded in this sense in Britain in 1925) are both common—though not equally common. The shorter “equal opportunity” is more popular, according to Google’s Ngram viewer.
The noun phrase “equal-opportunity employer” originated in the US in the 1960s, the OED says. Oxford’s definition is “one who professes not to discriminate against applicants or employees on such grounds”—that is, “race, gender, physical or mental handicap, etc.”
As we said above, the Latin adjective aequus gave us many English words beside “equity” and “equality.” We already mentioned “equal,” which was first recorded in a scientific work by Geoffrey Chaucer in 1391.
A passage in A Treatise on the Astrolabe (1391) explains how to regulate the complex astronomical instrument, and Chaucer uses “howres equales” and “howres in-equales” to mean “equal hours” and “unequal hours.”
That early use of “equal” retains a whiff of the Latin aequālis in its spelling, “equales”; the modern spelling didn’t appear until the 16th century.
Other English words that can be traced to aequus include “iniquity” (1300s); “equation” (1393); “equator” (circa 1400); “equinox” (c. 1400); “equate” (1400s); “equivalent” (c. 1460); “equalize” (1500s); “equidistant” (probably before 1560); “equivocate” (1590); “equivocal” (1601-02); “equanimity” (1607); “adequate” (1608) and “inadequate” (1675); “equilibrium” (1608); “equable” (1643); and a latecomer, “egalitarian” (1885).