Definition of selection rule
: a rule that states which of all the conceivable changes in the state of a quantized system (atoms, nuclei, or related entities) are physically possible under specified circumstances usually in terms of the possible numerical changes in the quantum numbers that characterize the system — compare allowed, forbidden
Love words? Need even more definitions?Merriam-Webster unabridged
Words at Play
- Words We're Watching: 'Samesies'
- The Good, The Bad, & The Semantically Imprecise - 10/18/19
- Noah Webster's Spelling Wins and Fails
- The Disputed Origins of the 'Egg Cream'
Ask the Editors
- Why Do People Pronounce It "Nucular"?
- On Contractions of Multiple Words
- Is Singular 'They' a Better Choice?
- Where in the World? A Quiz Take the quiz
- Advanced Vocabulary Quiz Take the quiz
- Spell It Take the quiz
- Bee Cubed Play the game