Key light - Wikipedia

File:Garden Key Light FL1.jpg - Wikipedia

Cedar Key Light - Wikiwand

I think might be the key. and why these interact at all, with particles containing mass

Photography and Graphic Technical Blog: Low-Key and High-Key lighting

Acceptance is key”: Thoughts on Pride Month and the Road to Equality from a Scarlet Knight – The Hilltopper

Jerusalem moves forward with urban renewal plans in key neighborhoods

Timeline of lighting technology - Wikipedia

The Town of Light review: A grim and unblinking psychological horror

Laser lighting display - Wikipedia