Other forms: seas
The sea is the huge body of salt water covering most of the planet. By the sea, at sea, the North Sea.
In British English sea is the ordinary word and ocean the geographic one for the five great divisions. At sea means both on a voyage and, figuratively, thoroughly confused: all at sea. Note sea level, sea change, meaning a complete transformation, from Shakespeare; sea legs; and that about seventy per cent of the planet is sea and roughly a fifth of it has been mapped in detail.
1nounseaThe huge body of salt water covering most of the planet.
“We swam in the sea every day on holiday.”
sea is a body of salt water.
Old English sae is Germanic and its deeper root is unknown, which is remarkable for a people who lived beside it. Latin used mare, giving marine and maritime, so English again has a native word and a borrowed technical one.
Proto-Germanic
*saiwiz
Proto-West Germanic
*saiwi — body of water
Old English
sǣ
Middle English
see
English, today
sea
Middle English see, from Old English sǣ, from Proto-West Germanic saiwi (“body of water”), from Proto-Germanic saiwiz, itself either:
Etymology from Wiktionary, CC BY-SA