Blocking can be defined as the non-occurrence of some linguistic form, whose existence could be expected on general grounds, due to the existence of a rival form. *Oxes, for example, is blocked by oxen, *stealer by thief. Although blocking is closely associated with morphology, in reality the competing “forms” can not only be morphemes or words, but can also be syntactic units. In German, for example, the compound Rotwein ‘red wine’ blocks the phrasal unit *roter Wein (in the relevant sense), just as the phrasal unit rote Rübe ‘beetroot; lit. red beet’ blocks the compound *Rotrübe. In these examples, one crucial factor determining blocking is synonymy; speakers apparently have a deep-rooted presumption against synonyms. Whether homonymy can also lead to a similar avoidance strategy, is still controversial. But even if homonymy blocking exists, it certainly is much less systematic than synonymy blocking.
In all the examples mentioned above, it is a word stored in the mental lexicon that blocks a rival formation. However, besides such cases of lexical blocking, one can observe blocking among productive patterns. Dutch has three suffixes for deriving agent nouns from verbal bases, -er, -der, and -aar. Of these three suffixes, the first one is the default choice, while -der and -aar are chosen in very specific phonological environments: as Geert Booij describes in The Morphology of Dutch (2002), “the suffix -aar occurs after stems ending in a coronal sonorant consonant preceded by schwa, and -der occurs after stems ending in /r/” (p. 122). Contrary to lexical blocking, the effect of this kind of pattern blocking does not depend on words stored in the mental lexicon and their token frequency but on abstract features (in the case at hand, phonological features).
Blocking was first recognized by the Indian grammarian Pāṇini in the 5th or 4th century
Construction Morphology is a theory of word structure in which the complex words of a language are analyzed as constructions, that is, systematic pairings of form and meaning. These pairings are analyzed within a Tripartite Parallel Architecture conception of grammar. This presupposes a word-based approach to the analysis of morphological structure and a strong dependence on paradigmatic relations between words. The lexicon contains both words and the constructional schemas they are instantiations of. Words and schemas are organized in a hierarchical network, with intermediate layers of subschemas. These schemas have a motivating function with respect to existing complex words and specify how new complex words can be formed.
The consequence of this view of morphology is that there is no sharp boundary between lexicon and grammar. In addition, the use of morphological patterns may also depend on specific syntactic constructions (construction-dependent morphology).
This theory of lexical relatedness also provides insight into language change such as the use of obsolete case markers as markers of specific constructions, the change of words into affixes, and the debonding of word constituents into independent words. Studies of language acquisition and word processing confirm this view of the lexicon and the nature of lexical knowledge.
Construction Morphology is also well equipped for dealing with inflection and the relationships between the cells of inflectional paradigms, because it can express how morphological schemas are related paradigmatically.