The long wait for =Sourced
The equals sign appeared in 1557.
Its next printed use came 61 years later.
Welsh mathematician Robert Recorde introduced = in a 1557 book, choosing two parallel lines to represent equality. The next known printed use came in 1618. Wider acceptance took longer still.
Even an everyday symbol
had a slow beginning.
Summary / translation: Unbubly · CC BY-SA 4.0
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Equality (mathematics) · Wikimedia contributors
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Reviewed: 2026-10-01