Full Idea
If a prototype of grandmothers represents them as grey-haired old women, and a definition of grandmothers represents them as being necessarily the mother of a parent ....we may fail to recognise that 'grandmother' represents two distinct concepts.
Gist of Idea
The word 'grandmother' may be two concepts, with a prototype and a definition
Source
Edouard Machery (Doing Without Concepts [2009], 3.3.4)
Book Reference
Machery,Edouard: 'Doing Without Concepts' [OUP 2009], p.74
A Reaction
He is referring to two distinct theories about what a concept is. He argues that both theories apply, so words do indeed represent several different concepts. Nice example.