# photoinitiator

> English word · Noun

## Definitions
1. Any substance that initiates a chemical reaction by the absorption of a photon to form an excited state.

## Etymology
From photo- + initiator.

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