/ɪnˈflɛkʃən/
Every time you bend your voice to ask a question, you are performing an act of ancient Roman grammar.
The word 'inflexion' — the preferred British spelling of the American 'inflection' — descends from the Latin *inflexio*, itself built from the verb *inflectere*: *in-* meaning 'into' or 'upon', and *flectere*, meaning 'to bend'. The Romans used *flectere* both literally, for the physical bending of objects, and grammatically, for the bending of words into their various forms. To inflect a verb was, in the Roman mind, to curve it — to take the straight stem and bend it into the shapes that tense, person, and number demanded.
The root *flectere* is ancient and productive, yielding a remarkable family of descendants that have shaped English in ways most speakers never notice. From it came *reflexus* (bent back), giving us 'reflex'; *deflectere* (to bend away), giving us 'deflect'; and *flexibilis*, meaning capable of bending, which became our 'flexible'. There is something almost physical about this entire word family — a sense of yielding, of yielding without breaking — and it persists even in abstract uses like 'inflection point', where something in a graph or a life or an economy bends and takes a new direction.
The word entered English in the sixteenth century, initially in the grammatical sense, borrowed through scholarly Latin at a time when English writers were busily enriching their language with classical borrowings. Early grammarians used it to describe what happened to Latin nouns and verbs as they changed their endings according to syntactic role — the bending of *amicus* into *amici* or *amico* or *amicum*. It was a concept rooted in Latin's own highly inflected nature, though English grammarians soon began applying it to the much simpler workings of their own tongue.
Over time, the word's reach expanded generously beyond grammar. By the seventeenth and eighteenth centuries, writers on rhetoric and music had adopted 'inflexion' to describe the modulation of the voice — the rises and falls of pitch and tone that give speech its expressiveness and music its emotional contour. When you hear that someone speaks 'without inflexion', the image is of a voice that refuses to bend, that remains rigid and unmodulated, as flat and unyielding as an untuned string. The grammatical metaphor had curved its way beautifully into aesthetics.
The spelling difference between 'inflexion' and 'inflection' is itself a minor historical accident. Both forms appeared in early modern English, with *-xion* and *-ction* endings competing for supremacy in various Latin-derived words. British English tended to preserve the *-xion* form in words like 'connexion', 'complexion', and 'inflexion', while American English largely standardised on *-ction*. Today 'inflexion' remains the dominant form in British dictionaries and publishing, a quiet marker of orthographic tradition that is itself a kind of inflection — a bending of spelling toward a different cultural axis.
In modern usage, 'inflexion point' has taken on a powerful new life in business, economics, and technology, describing the moment when a trend changes its direction of curvature — borrowed from the mathematical sense, where an inflection point is precisely where a curve changes from concave to convex. This technical precision sits alongside the vocal and grammatical senses, giving the word a range that stretches from the classroom to the boardroom, from the tongue of a Roman orator to the charts of a Silicon Valley strategist. The bending metaphor, it turns out, has proven remarkably flexible.