# sesquiennial

> English word · Adjective

## Definitions
1. Occurring once every one and a half years (i.e. once every 18 months, or twice every three years); sesquiannual.

## Etymology
From Latin sesquiennium (compare sesqui- and biennial).

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/sesquiennial