/tuː/ (stressed), /tə/ (unstressed)
[preposition/particle] A small word used to show direction, purpose, or a relationship between things — for example, moving toward something, or connecting a verb to its object. It is also used before verbs to form the infinitive, as in 'to run' or 'to think'.
One of the oldest words in English, 'to' has barely changed in spelling or sound for over a thousand years.
The word 'to' is one of the oldest survivors in the English language, stretching back without interruption to Old English, where it appeared as 'tō'. It was used then in almost exactly the same ways it is used today — to indicate direction, destination, and purpose. Old English 'tō' could mean 'toward', 'in the direction of', or 'for the purpose of', and speakers of the language would have found the word utterly familiar in sentences that look recognisable even now.
The Old English form 'tō' descended from Proto-Germanic '*tō' or '*da', a directional particle shared across the Germanic family of languages. Its cousins are still visible today: German 'zu', Dutch 'toe', Old Norse 'til', and Old Frisian 'to' all come from the same ancient root. This tells us that the word was already well established before the Germanic tribes separated and spread across Europe, meaning it is at least two thousand years old as a concept, even if the written records only go back about twelve centuries.
Tracking even further back, linguists connect the Proto-Germanic root to the Proto-Indo-European particle '*do-' or '*de-', which expressed ideas of movement and direction. This ancient root is the common ancestor of a remarkable range of words across many languages, though the connections are sometimes hard to see on the surface. The idea of 'moving toward a point' appears to be one of the most fundamental things early human language needed to express, and 'to' is English's ancient answer to that need.
What is especially striking about 'to' is how stable it has been. While thousands of English words have changed dramatically in spelling, pronunciation, and meaning over the centuries — often becoming almost unrecognisable — 'to' has remained essentially the same. The Great Vowel Shift of the 15th and 16th centuries, which transformed the pronunciation of nearly every long vowel in English, barely touched this little word. Its very smallness and frequency may have protected it: words used constantly by everyone tend to resist change because any shift would cause immediate confusion.
The use of 'to' as an infinitive marker — the 'to' in phrases like 'to love', 'to dream', or 'to eat' — developed gradually through the Old and Middle English periods. Originally, Old English expressed infinitives with verb endings alone, without needing 'to' in front of them. But as those endings eroded during the Middle English period, 'to' stepped in to carry the grammatical weight instead. By the time Chaucer was writing in the late 14th century, the 'to-infinitive' was firmly established, and it has remained a cornerstone of English grammar ever since.
Today, 'to' is one of the most frequently used words in the entire English language — typically ranking in the top three or four in any large collection of written or spoken English text. It is so common that we use it dozens of times in a single conversation without noticing. Yet behind this invisible, unassuming little word lies more than a thousand years of unbroken use, a family of related forms spread across a continent, and a grammatical history that quietly shaped the way English sentences are built.