are

The word 'are' — the plural present tense of 'to be' — has a more turbulent history than its ubiquity suggests.‌​‌​‍​‌​‍​‌​‍​‌​‌​‌​‍​‍​‍​‍​‍​‍​‌​‌​‍​‌​‍​‍​‌​‍​‍​‍​‌​‍​‍​‌​‌​‌ It represents a dialectal form that was originally confined to northern England and gradually displaced the original southern form over several centuries.

In Old English, the paradigm of 'beon/wesan' (to be) used forms from PIE *h₁es- for the plural present: 'sindon' or 'sind' (they are). This is cognate with German 'sind' (they are), which preserves the original form to this day. The Northumbrian dialect of Old English, however, used different forms: 'earun' or 'aron' (they are), from Proto-Germanic *ar-, a form whose ultimate PIE etymology is debated — it may connect to *h₁er- (to move, to arise) or represent an extended form of *h₁es-.

During the Middle English period (roughly 1100-1500), the northern 'aron/aren' forms spread steadily southward. This expansion was likely accelerated by the heavy Old Norse influence in northern England (the Danelaw), where the Norse cognate forms reinforced the native Northumbrian ones. By the thirteenth century, 'aren' had reached the Midlands. By the fourteenth century, it appears in London texts. By the fifteenth century, 'sindon' was extinct, and 'are' was the undisputed plural form.

This is a rare case of a non-prestige dialect form conquering the prestige dialect. Normally, standard forms (based on the speech of London and the southeast) replace regional variants. With 'are,' the flow was reversed — perhaps because the original 'sindon' was already weakening, and the northern form filled a vacuum.

The second-person singular 'art' (thou art) comes from the same root — Old English 'eart' — and survived into Early Modern English before falling out of use along with 'thou' itself. It persists in literary and religious language ('thou art') and in the King James Bible.

The Scandinavian cognates are revealing: Icelandic 'er' (is/are), Swedish 'ar' (is), Norwegian 'er' (is/are) all descend from the same Proto-Germanic *ar- forms. In these North Germanic languages, the *ar- forms became the standard present tense for all persons, not just the plural — a more thoroughgoing victory than in English, where 'am' and 'is' survived from the competing *h₁es- root.

The story of 'are' is thus the story of a dialectal insurgency: a northern form, reinforced by Norse contact, spreading south to displace an older, established paradigm. Modern Standard English preserves the result — every time you say 'we are' or 'they are,' you are using a word that was, a thousand years ago, a regional variant that most speakers of Old English would not have recognized as standard.