# Different spacing caused by \newcommand and \def [closed]

From the answer to my other question " define something like \lim but for another name", I tried:

\def\ext{\qopname\relax m{ext}}


and:

\newcommand{\ext}{\qopname\relax m{ext}}



But actually they do not. For the \def case, it seems to add extra spacing around \ext when I use it (just like \lim would). And \newcommand does not.

Why? What exactly is the different behavior for those more generally?

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## closed as not a real question by Martin Scharrer♦Mar 16 '11 at 14:07

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Can you post a screenshot? I just tried it, and I thought I could see the difference on one test but when I zoomed in then it disappeared. –  Loop Space Mar 16 '11 at 10:22
I think in general normal users should stay way from \def as it overwrites existing macros without question. Usually one should only overwrite a macro if on know what it does and one is certain it will be OK to overwrite it. The classical example is of course \span –  daleif Mar 16 '11 at 10:27
@Martin: Hm, I just tried. But I don't seem to be able to reproduce this. Maybe it was something different and lead me to this wrong conclusion. –  Albert Mar 16 '11 at 10:36
@Martin: I don't really want to delete it in the case that I stumble again upon it and when I am able to reproduce it. I would close it for now and reopen it later then. But I don't know how to do that. Maybe I lack enough reputation. –  Albert Mar 16 '11 at 14:06