https://www.cut-the-knot.org/do_you_know/addition.shtml#groupoid

where it is described as a set with a binary operation
which is not necessarily associative.

Most mathematicians use the term "groupoid" for something
else: a category in which every morphism is invertible.
In rough but more down to earth terms, a groupoid is a
structure with a partially defined multiplication (usually
called "composition" which *is* associative where defined,
and which has an appropriate inversion operation, much like
a group. (See any primer on category theory for more info.)

Most mathematicians call a thingy with a not-necessarily
associative binary operation a "magma". Kind of amorphous-like.

duffifi

Many thanks for the kind words.

>but
>I did have a comment on the entry for "groupoid":
>
>https://www.cut-the-knot.org/do_you_know/addition.shtml#groupoid
>
>where it is described as a set with a binary operation
>which is not necessarily associative.
>
>Most mathematicians use the term "groupoid" for something
>else: a category in which every morphism is invertible.
>In rough but more down to earth terms, a groupoid is a
>structure with a partially defined multiplication (usually
>called "composition" which *is* associative where defined,
>and which has an appropriate inversion operation, much like
>a group. (See any primer on category theory for more info.)
>
>Most mathematicians call a thingy with a not-necessarily
>associative binary operation a "magma". Kind of
>amorphous-like.
>
I believe that at the time I might have had my last chance to dig into algebra at the groupoid level, the word "magma" was not yet appropriated for that purpose.

I'll find a way to mention the fact on the relevant page. Thank you again.