a symbol in a logical or mathematical expression that can be replaced by the name of any member of specified set | the semantic role of the animate entity that instigates or causes the happening denoted by the verb in the clause |
a person authorized to act for another | an active and efficient cause; capable of producing a certain effect |
| a businessman who buys or sells for another in exchange for a commission |
| a representative who acts on behalf of other persons or organizations |
| any agent or representative of a federal agency or bureau |
| a substance that exerts some force or effect |