The document discusses the concepts of rule productivity, exceptions and suppletions, and lexical gaps in morphology. It provides examples to illustrate each concept.
Rule productivity refers to the ability of an affix or morphological process to coin new complex words according to the rules of a language. Highly productive rules like suffixation with -ing or plural -s are regularly used to form new words. Exceptions and suppletions are instances that do not follow regular morphological rules, such as irregular verb forms. Lexical gaps are words that are permitted by grammar rules but do not exist, such as potential words that are phonologically or semantically possible but not present in the lexicon.