Question: why error takes argument without ()?

What is the reason that error accepts its arguments without being inside paranthesis? This is different from all other Maple functions I've seen. For example, both these below work the same

f := proc (x) 
     if x<0 then 
        error "invalid x: %1", x; 
     else 
        x^(1/2); 
     end if 
end proc:

And

g := proc (x) 
     if x<0 then 
        error("invalid x: %1", x); 
     else 
        x^(1/2)
     end if 
end proc:

One can't do for other Maple functions. For example sin x  gives an error. It must be sin(x)

Looked at help page for error and did not see something about this difference.

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