- irrationality condition
- irrationality estimate
- irrationality exponent
- irrationality measure
- irrationality sequence
- irrational number
- irrational number theorem
- irrational quantity
- irrational root
- irrational rotation algebra
- irrational rotation (C*) algebra
- irrational rotation C* algebra
- irrational rotation number
- irrational spin
- Irrational will
- Irrawaddy Delta
- Irrawaddy River
- irrealis mood
- irrecoverable
- irredeemable
- irreducibility
- irreducibility criterion
- irreducibility theorem
- irreducible
- irreducible 3 manifold