Activation energy (Ea) is the minimum amount of energy required for a chemical reaction to occur. It determines the rate at which reactants transform into products.
Catalyst: A substance that increases the rate of a chemical reaction by lowering its activation energy without being consumed.
Arrhenius Equation: $k = A e^{-E_a/RT}$; an equation that shows how the rate constant ($k$) of a reaction depends on temperature ($T$) and activation energy ($E_a$).
Transition State: A high-energy state during a chemical reaction where old bonds are breaking and new bonds are forming.