From PIE *h1esti — nearly identical in Sanskrit, Greek, Latin, and German across 6,000 years.
Third person singular present of 'be'; used to indicate identity, existence, or a quality.
From Old English is (third person singular present of bēon, to be), from Proto-Germanic *isti (is), from the PIE root *h₁es- (to be, to exist). This root is the most fundamental verb in Indo-European and one of the most extensively studied in historical linguistics. From *h₁es- came Latin esse (to be — hence English essence, essential, absent, present, entity, interest), Latin est (he/she is), Greek esti (is), Greek einai (to be — hence English ontology), Sanskrit ásti (is), Old Persian astiy (is — as in the Behistun inscription), Lithuanian esti (is), Old Church Slavonic jestŭ (is), Hittite ēšzi (is — the oldest attested form, c. 1600 BCE), and Armenian ē (is). The English verb to be is
PIE *h₁ésti → Sanskrit 'ásti' → Greek 'estí' → Latin 'est' → German 'ist' → English 'is.' Six thousand years, six languages, and the word has barely changed. 'Is' may be the most stable word in any human language — the sound you make to say 'exists' has been nearly identical since the Bronze