/ɑːr/ (stressed), /ər/ (unstressed)
[verb] The second person singular and all plural forms of the verb 'to be', used to say that something exists or to describe a state. For example: 'You are ready' or 'They are here.'
'Are' and 'is' come from completely different ancient verbs — English quietly stitched two unrelated words into one.
The word 'are' has one of the most surprisingly tangled histories in the English language. It looks simple — just three letters, one of the most common words a person will ever type or speak — yet it is the product of a remarkable linguistic process called suppletion, in which different words from entirely separate roots are combined to fill out the forms of a single verb. The modern verb 'to be' is not descended from one ancient word. It is a patchwork, assembled over millennia from at least three distinct Proto-Indo-European roots.
The direct ancestor of 'are' is the Old English word 'earun' or 'aron', which was used in the north of England, particularly in Northumbrian dialects. This form came from Proto-Germanic *arun, which itself traces back to the Proto-Indo-European root *h₁es-, meaning 'to be' or 'to exist'. This is one of the oldest and most widely travelled roots in the entire Indo-European family. It gave Sanskrit 'asti' (he is), Greek 'esti' (he is), and Latin 'est' (he is) — though these cousins went their separate ways thousands of years ago.
Interestingly, 'are' was not always the standard English form. In the Old English of southern England — the variety used in most written records — the equivalent plural form was 'sindon' or 'sint', descended from yet another ancient root. The form 'are' gradually spread southward from northern and Midland dialects during the Middle English period (roughly 12th to 15th centuries), eventually replacing the older southern forms entirely. By the time of Geoffrey Chaucer in the late 14th century, 'are' was already common in written English, and by the Early Modern English period — the language of Shakespeare — it had become fully established.
Meanwhile, the other parts of the verb 'to be' were assembled from different sources. 'Is' comes from a separate Proto-Indo-European root *h₁esti, via Old English 'is'. 'Was' and 'were' come from yet another ancient root, Proto-Indo-European *wes-, meaning 'to dwell' or 'to remain', which gave Old English 'wæs' and 'wæron'. And 'be' itself comes from a third root, *bʰuH-, meaning 'to grow' or 'to become', which also gave us 'been' and 'being'. In other words, when you say 'I was, you are, she has been', you are unknowingly using three ancient and unrelated verbs as if they were one.
This kind of grammatical fusion is rare but not unique — Latin 'ferre' (to carry) and English 'go/went' show similar patchwork constructions. But the verb 'to be' is perhaps the most extreme example in common English use. What makes 'are' particularly striking is how thoroughly it erased its competition. The old southern plural forms vanished so completely that almost no speaker today knows they ever existed. Three letters, spoken hundreds of times a day, carry within them the echo of a Proto-Indo-European root that humans were using to describe existence long before writing was invented.