The aim of this article is to complete and systematize affixal meaning definitions by examining the Old English derived nominal and adjectival lexicon from a structural-functional framework. The main dictionaries of reference in this language have proven to contribute limited affixal information; besides, one and the same dictionary organizes its affixal entries quite dissimilarly both formally and content-wise. Given this background, the present work offers an insight into the derived lexicon and suggests more accurate definitions based on an approach that explains form and meaning associations in terms of lexical functions and macrofunctions. The data of analysis have been retrieved from the lexical database of Old English Nerthus, which has supplied the inventory of affixes and of affixed nouns and adjectives performing a lexical function belonging to the semantic categories quantity, size or rank, which apply whenever an entity or a property experience an increase or a decrease in quantity, quality or status respectively. Each affix is defined conforming to the different meanings it conveys, the source and target categories involved in the derivation process and the predicates that fit the rule in each case. An approach based on form and meaning associations in the definition of affixal meaning has demonstrated to have major implications not only in the field of lexicology but also of lexicography inasmuch as it permits to revise, complete and enhance dictionary entries and gain systematicity in the manner the information is rendered.