/ˈæksɪdəns/
[noun] The part of grammar that deals with how words change their form — for example, how verbs change to show tense, or how nouns change to show plural. It is the study of inflection, the small but important changes in word endings that carry meaning.
This grammar word was born from a mistranslation — Latin philosophers used 'accidents' to mean changeable qualities, and grammarians borrowed the idea for changeable word endings.
The story of 'accidence' begins not in a schoolroom but in ancient Greek philosophy. Aristotle used the word *symbebēkos* to describe qualities that belong to a thing but are not essential to it — a man may be pale or dark, tall or short, and he is still a man. These changeable, non-essential properties were his 'accidents.' When Roman thinkers translated Aristotle into Latin, they reached for *accidens*, the present participle of *accidere*, meaning 'to happen' or 'to fall upon' — from *ad-* (to) and *cadere* (to fall). An 'accident,' in this original philosophical sense, was simply something that 'fell upon' a thing without being part of its core nature.
Latin grammarians then made a brilliant leap of borrowing. Just as Aristotle's accidents were the variable, non-essential features of objects, the grammatical forms of words — their endings, their inflections — seemed similarly variable and changeable. The word *accidentia* (plural of *accidens*) was applied to these changeable word properties: tense, case, gender, number. The great Roman grammarian Priscian, writing in the 6th century AD, used *accidentia* systematically to describe the properties that 'happen to' nouns and verbs — the qualities that change while the root of the word remains the same.
This Latin grammatical tradition passed into medieval Europe through the works of scholars who wrote in Latin and taught grammar as one of the foundational arts. The term *accidentia* became a standard piece of grammatical vocabulary across medieval schools, where learning Latin grammar was the first serious intellectual task of any student's education. It was in this educational context that the word began its journey toward English, carried along by centuries of classroom use.
The word entered English in the 15th century, appearing in early printed grammar books and educational texts. It arrived essentially as a direct borrowing from Medieval Latin *accidentia*, with the ending reshaped to the familiar English suffix *-ence*. William Lily's famous Latin grammar — the 'Short Introduction of Grammar' authorised by Henry VIII in 1542 and used in English schools for over two centuries — helped cement 'accidence' as the standard English term for the inflectional section of grammar. Children learning their Latin declensions and conjugations were learning their 'accidence' before they moved on to 'syntax.'
Over time, 'accidence' came to refer specifically to elementary grammar — not just inflection in the technical sense, but the whole first stage of language learning. It became associated with beginners, with the most basic and foundational rules. By the 17th and 18th centuries, books called 'An Accidence' or 'The Accidence' were essentially primers, the ABCs of language learning. The word quietly narrowed its meaning from a rich philosophical concept to a modest classroom term. Today it is rarely used outside specialist discussions of historical grammar or linguistics, yet it carries within it the whole philosophical tradition of Aristotle, the scholarship of Priscian, and centuries of children puzzling over Latin verb endings.