# permethrin

> English word · Noun

## Definitions
1. A synthetic insecticide, C₂₁H₂₀Cl₂O₃, used to treat head lice, nits, and scabies; as an active ingredient in flea collars; and to eradicate woodworm infestations.

## Etymology
From Latin perme(ō) (“to pervade”) + -thrin.

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