What you see would indicate that this string is missing from your language file, not that it is not translated. Could be the problem is in special characters, in that case try writing heading label without those characters and adjust language string.

Hello Klas

Yes, this is what I tried first but without sucess. The string does exist since it is a standard joomla seblod field (art_catid) and in another list it is well translated. so the string is not missing in the language file

COM_CCK_CATEGORY="Catégorie"

BUT in this list there is a heading on the field and once there is a heading the label is translated as "COM_CCK_Catégorie" 

thanks

cyril

Just use CATEGORY (or any other english string that you have in the language file without com_cck prefix ).

I tested and it seem by default heading label is not translated at all in 3.8.4 . But it Works correctly if I set typography to Heading.

sorry, VARIATION, not typography..