Full Idea
The word 'knife' names an object in respect of its function. That is not to say (simply) that it names an object which has a function, but also that the function is involved in the meaning of the word.
Gist of Idea
Some words, such as 'knife', have a meaning which involves its function
Source
Philippa Foot (Goodness and Choice [1961], p.134)
Book Reference
Foot,Philippa: 'Virtues and Vices' [Blackwell 1981], p.134
A Reaction
It seems faintly possible that someone (a child, perhaps) could know the word and recognise the object, but not know what the object is for. Ditto with other things which have functional names.