aware of the term, but they almost never use improper classes.

&gt; In the 
&gt;wider word, however, the term "class" is used in a sense which is 
&gt;closely linked to "classification", to refer to (the extension of) a 
&gt;named category in some kind of classification heirarchy. Such classes 
&gt;all have sets as their extension (or, maybe, ARE sets), but not every 
&gt;set would normally be dignified with the title of 'class(ification)'

This is another common use.  But in the programming language
commu