is a symbol or symbols denoting an operation in an expression or formula:

*Simple*

`+`

(addition), `-`

(subtraction), `*`

(multiplication or product), `/`

(division or nesting), `.`

(interaction), `=`

(assignment), `<`

(less than), `>`

(greater than)

*Compound*

`**`

(exponentiation), `*+`

(matrix multiplication), `-*`

(crossed deletion), `-/`

(nested deletion), `//`

(pseudo-term linkage), `.EQ.`

or `==`

(equality), `.NE.`

or `/=`

or ` (non-equality), `

`.LE.`

or `<=`

(less than or equal to), `.GE.`

or `>=`

(greater than or equal to), `.LT.`

(less than), `.GT.`

(greater than), `.EQS.`

(string equality), `.NES.`

(string non-equality), `.IN.`

(set inclusion), `.NI.`

(set non-inclusion), `.IS.`

(identifier equivalence), `.ISNT.`

(identifier non-equivalence), `.AND.`

(logical *and*), `.OR.`

(logical *or*), `.EOR.`

(logical *either or*), `.NOT.`

(logical *not*).

Only` + - * / . -/ -* `

and` // `

may occur in formulae, while` . -* -/ `

and` // `

cannot occur (as operators) in expressions.

*Precedence*

The list below shows the order in which the operators are evaluated when they are used in expressions, if brackets are not used to make the order explicit:

(1) `.NOT.`

Monadic `-`

(2) `.IS. .ISNT. .IN. .NI. *+`

(3) `**`

(4) `* /`

(5) `+`

Dyadic `-`

(6) ` == = /= .LT. .GT. .EQ. .LE. .GE. .NE. .NES.`

(7) `.AND. .OR. .EOR.`

(8) `=`

(*Monadic minus* means the use of the minus sign in a negative number: for example, -1.) Within each class, operations are done from left to right within a expression, unless brackets are used to indicate some other order.