Rho
The sensitivity of an option's price to a 1-percentage-point change in the risk-free interest rate.
ρ = ∂V / ∂r (change in option value per 1% change in risk-free rate)
Rho measures the impact of interest rate changes on an option's price. A call with rho of 0.05 gains $5 per contract for a 1% rise in rates; puts have negative rho.
For short-dated equity options, rho is the least significant of the main Greeks — a 25 basis point rate move barely nudges a 30-day option's value. Rho becomes more meaningful for long-dated options (LEAPS) and interest-rate derivatives where rate sensitivity is the core driver.