Texas Instruments TI-99/4A - Page 127

DEF
If you specify a parameter when defining a function, you must
specify an argument when you reference the function. Similarly, if
you do not specify a
parameter when defining a function, you cannot
specify an argument in the function reference.
User's Reference Guide
Examples:
>NEW
>100 OEf SQUARE(Xl=X*X
>110 PR1NT SQUARE
>120 END
>RUN
* NAME CONfLICT IN 110
>100 DEf Pl=3.1416
>110 PR1NT pI(Z)
>RUN
* NAME CONfLICT lN 110
11,107