(1) A program statement that specifies an operation to be performed by the computer, along with the values or locations of operands. This statement represents the programmer's request to the processor to perform a specific operation. [1]
(2) In COBOL, one or more clauses, the first of which starts with a keyword that identifies the instruction. Instructions affect the flow of control, provide services to the programmer, or both.
(3) In REXX, one or more clauses that describe some course of action to be taken by the language processor. Instructions may be assignments, keyword instructions, or commands.