Word-based and meaning-based approaches to definition
The definitions found in dictionaries are the result of a word-based, or semasiological approach to meaning. This sort of approach starts with a language’s individual lexemes, and tries to specify the meaning of each one. This is not the only possibility, however, for the analysis of meaning in linguistics. The other approach, the onomasiological one, has the opposite logic: start with a particular meaning, and list the various forms available in the language for its expression. Thus, whereas a semasiological analysis would start with a list of verbs, say scare, frighten, terrify, startle, spook, and panic, and specify a slightly different meaning for each (startle, for instance, referring to a considerably weaker form of alarm than panic), an ono masiological analysis would start with a general concept, FRIGHTEN, and list all of these verbs as its possible realizations. The difference between the two approaches corresponds to the difference between a dictionary and a thesaurus. As a semasiological tool, a dictionary is a list of words, and one accesses meanings through words. A thesaurus, on the other hand, is a list of concepts: for a particular concept, the thesaurus gives access to the different words through which the concept could be expressed.
Semasiological and onomasiological analysis are in no way exclusive: the semasiological approach emphasizes differences between lexemes, the onomasiological one similarities. Furthermore, both are necessary to a full description of the processes underlying communication. A complete description of linguistic performance will show how a speaker achieves the mapping between the concept or meaning she wishes to express and the word forms actually chosen: given the need to express the concept or meaning FRIGHTEN, for example, what are the onomasiological principles according to which one of the possible verbs listed above is chosen? For the hearer, however, a semasio logical approach is called for. Hearing or reading the word frighten in a particular context, what is the meaning which the hearer will assign to this verb?
