Polyfunctionality

Polyfunctionality is the phenomenon that one affix is used with a number of different meanings or grammatical functions.

Example
In Dutch, the suffix -er is used to form
 * 1) deverbal agent nouns (werker 'worker),
 * 2) deverbal instrument nouns (wekker 'alarm clock'),
 * 3) geographical personal nouns (Amsterdammer 'person living in Amsterdam'),
 * 4) denominal personal nouns (rechter 'judge'), and (e) deadjectival personal nouns (ouder 'parent').

Links
Utrecht Lexicon of Linguistics