реагент означава в английски

reactant [reactants]▼(participant at the start of a chemical reaction)
noun
[UK: ri.ˈæk.tənt] [US: ri.ˈæk.tənt]

reactor [reactors]▼(chemical substance which responds to another substance)
noun
[UK: rɪ.ˈæk.tə(r)] [US: ri.ˈæk.tər]