This journal article draws a distinction between the split and unified functions obtaining in the formation of Old English nouns and adjectives. The starting point of the discussion is an enlarged inventory of lexical functions that draw on Meaning-Text Theory and structural-functional grammars and explain the change of meaning caused by prefixation and suffixation in Old English. The extended inventory of lexical functions consists of 33 functions and has been applied to ca. 7,500 affixed nouns and adjectives extracted from the lexical database Nerthus (www.nerthusproject.com). The distinction between split and unified functions, in such a way that the former can be realized by both prefixes and suffixes and the latter by either prefixation or suffixation, allows for some generalizations. Firstly, the analysis proves that there are more functions involved in prefixation than in suffixation. Secondly, prefixation is meaning oriented while suffixation is class oriented.