I truly appreciate your clarifications. 

Perhaps the following should be included in the documentation; "don't include a space between plot.... Maple treats the space as 'plot' mulitplied by(...)". 

I also thank you for pointing out the differences in the calling sequences. 

Thank you, djc.  I works withou the [ (square bracket),i.e. I got the plot.   

However it puzzles me, because the documentation states plot ([]).

Furthermore, my question is only a part of the parameteric equation that I have, which is:

x = exp(-t) +t ; y = exp(-t) -t     t= -2...2

I follow the syntax of plot for parametric, whicl is  plot ([]), with [ (square bracket).

Neither of the following would give me a plot:

plot (exp(-t) + t, exp(-t) - t, t=-2..2);   (no square brackets)

plot([exp(-t) + t, exp(-t) - t, t=-2..2]);  (with square brackets)

Thanks in advance for your help.

* or Shift-8 from the keyboard works.   Thank you, acer

The x is "times" from the Operators panel, which I thought it was a multiplication.  When the x (times from the Operators panel) can be used?