senate (n.)

c. 1200, "legal and administrative body of ancient Rome," from Old French senat or Latin senatus "highest council of the state in ancient Rome," literally "council of elders," from senex (genitive senis) "old man, old" (from PIE root *sen- "old"). Attested from late 14c. in reference to governing bodies of free cities in Europe; of national governing bodies from 1550s; specific sense of upper house of U.S. legislature is recorded from 1775.

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Definitions of senate from WordNet
senate (n.)
assembly possessing high legislative powers;
Senate (n.)
the upper house of the United States Congress;
Synonyms: United States Senate / U.S. Senate / US Senate