/ðɛn/
[adverb] Used to talk about a particular time in the past or future, or to show that one thing happens after another. It can also mean 'in that case' or 'as a result of that'.
'Then' and 'than' were once the exact same word — English only separated them into two over the centuries.
Few words in English are as quietly ancient as 'then'. It descends directly from the Old English word 'þonne' (and its close variant 'þanne'), which carried the same broad meanings it does today — marking time, showing sequence, and drawing logical conclusions. Old English 'þonne' came from Proto-Germanic *þana-, a demonstrative root built on the same base as words meaning 'that' and 'there'. This root was not unique to English; it spread widely across the Germanic family, appearing in Old High German 'danne', Old Saxon 'thanna', and Gothic 'þan', all meaning roughly 'at that time' or 'therefore'. The word's deep origins point toward Proto-Indo-European *to-, a root for demonstrative and pointing words found in languages across Europe and beyond.
The most surprising chapter in 'then's history is its long entanglement with the word 'than'. For most of the Old English and Middle English periods, these were not two words at all — they were one. The same form, 'þonne' or later 'than' or 'then', did double duty: it marked time ('he left then') and made comparisons ('she is taller than him'). Speakers felt no need to distinguish them because context made the meaning clear. The slow separation of 'then' and 'than' into distinct spellings with distinct jobs took centuries, and even in the 18th century writers and printers used the two forms interchangeably without anyone thinking it a mistake.
During the Middle English period, the Old English 'þonne' gradually softened. The 'þ' sound — the ancient letter called 'thorn', which made the 'th' sound — was eventually replaced in writing by the letter combination 'th', giving forms like 'thanne' and 'thenne'. The vowel shifted and shortened, and by the late Middle English period the word had settled into something very close to modern 'then'. Geoffrey Chaucer uses forms of the word throughout his writing in the late 14th century, confirming it was already a workhorse of everyday English, connecting events and conclusions just as it does today.
What makes 'then' so interesting from a linguistic point of view is how much work such a tiny word does. It is what linguists call a 'discourse marker' — a word that organises the structure of thought rather than carrying heavy meaning on its own. It can place an event in time ('we were young then'), signal a logical consequence ('if you're tired, then sleep'), show the next step in a sequence ('first stir, then bake'), or add an extra thought ('and then there's the cost'). Very few words in any language perform so many different roles with such ease, and 'then' has been doing all of them since before English had a name.
The family of words connected to 'then' through its Proto-Germanic root *þana- includes some surprising relatives. The Old English demonstratives 'þe' and 'þæt' — ancestors of 'the' and 'that' — are distant cousins, all built on the same pointing, indicating idea. Through the shared Proto-Indo-European root *to-, even more distant connections appear: the Latin word 'tam' (meaning 'so' or 'as'), and Sanskrit 'tad' (meaning 'that'), all echo the same ancient impulse — to point at something, whether in space, in time, or in logic. 'Then' is, at its heart, a word for pointing: not at a place, but at a moment.