In the manual, unless I am mistaken, it says to replace \si by \unit.

But I have this error:

Package siunitx Error: Found prefix part with no unit.

How can I make this document compatible with the new version 3 of siunitx?



%  \sisetup{color = blue}

  \begin{tabular}{l l l}
   kilo $=1000$ & noté \unit{\kilo} &\rule[2mm]{0pt}{5mm} Exemples:\ \unit{\kilo\metre}; \unit{\kilo\gram};% \\
%   hecto $=100$ & \repete{noté} \si{\hecto} &\rule[2mm]{0pt}{5mm}\repete{Exemple:}\ \  \si{\hecto\meter}; \si{\hecto\gram}; \si{\hecto\liter}\\
%   deca $=10$ & \repete{noté} \si{\deca}& \rule[2mm]{0pt}{5mm}\repete{Exemple:}\ \  \si{\deca\meter}; \si{\deca\gram}; \si{\deca\liter}\\
%      déci $=0.1=\dfrac{1}{10}$ & \repete{noté} \si{\deci} & \rule[2mm]{0pt}{5mm}\repete{Exemple:}\ \ \si{\deci\meter}; \si{\deci\gram}; \si{\deci\liter} \\
%   centi $=0.01=\dfrac{1}{100}$ & \repete{noté} \si{\centi} & \rule[2mm]{0pt}{5mm}\repete{Exemple:}\ \ \si{\centi\meter}; \si{\centi\gram}; \si{\centi\liter}\\
%    milli $=0.001=\dfrac{1}{1000}$ & \repete{noté} \si{\milli} & \rule[2mm]{0pt}{5mm}\repete{Exemple:}\ \ \si{\milli\meter}; \si{\milli\gram}; \si{\milli\liter}

  • 4
    \unit{\kilo} is the culprit: a prefix without unit.
    – egreg
    Sep 4, 2021 at 20:44

1 Answer 1


First off, you can use \si also with siunitx version 3, but it's deprecated and is present for back compatibility.

Second: a prefix must be followed by a unit; it wasn't enforced in version 2, now it is.

With a little stretch, you can define a \siprefix command:






You could actually do \unit{k}, but this would defy the purpose of the package.

  • You say that \si is back compatible but with version 3 \si{\kilo} doesn't work while it worked with version 2!
    – AndréC
    Sep 4, 2021 at 20:57
  • 3
    @AndréC It sort of worked. But the documentation has always been adamant in saying that prefixes must be followed by units.
    – egreg
    Sep 4, 2021 at 21:01
  • If I write \unit{k} instead of \unit{\kilo}, will the result be identical?
    – AndréC
    Sep 4, 2021 at 21:03
  • 2
    @AndréC Just type k.
    – egreg
    Sep 4, 2021 at 21:05
  • ok, can you add this possibility to your answer?
    – AndréC
    Sep 4, 2021 at 21:07

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