I think you want the "Duplicates" section of the "Kinds" chapter in the documentation (Writing with Inform). Here's a snippet, but there are more examples of varying complexity in that same section:
ยง4.14. Duplicates
Although it is only useful to a limited extent, we can make any number of copies of something:
"Polygons"
A shape is a kind of thing. A square is a kind of shape. A triangle is a kind of shape.
The Geometry Lab is a room. In the Geometry Lab are three triangles and two squares.
The description "three triangles" makes three identical things, each of the kind "triangle", and similarly for the squares. When the above is compiled, the player can type TAKE TWO TRIANGLES or TAKE ALL THE TRIANGLES and so forth.