A first order reaction is a type of chemical reaction where the rate of the reaction depends on the concentration of one reactant.
This is an equation that relates the rate of a reaction to the concentrations of its reactants. For first order reactions, it shows that rate is directly proportional to one reactant's concentration.
In context of first order reactions, this refers to the time it takes for half of a given amount of reactant to be consumed.
This is a proportionality constant in the rate law which reflects how quickly or slowly a reaction occurs.