This problem may be viewed in terms of the possible ways of classifying vocabulary items

В§ 51. Semantic Similarity of Morphemes and Word-Families

Lexical groups composed of words with semantically and phonemically identical root-morphemes are usually defined as word-families or word-clusters. The term itself implies close links between the members of the group.
Such are word-families of the type: lead, leader, leadership; dark, darken, darkness; form, formal, formality and others. It should be noted that members of a word-family as a rule belong to different parts of speech and are joined together only by the identity of root-morphemes. In the word-families discussed above the root-morphemes are identical not only in
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meaning but also in sound-form. There are cases, however, when the sound-form of root-morphemes may be different, as for example in sun, sunny, solar; mouth, oral, orally; brother, brotherly, fraternal, etc.; their semantic similarity however, makes it possible to include them in a word-family. In such cases it is usual to speak of lexical suppletion, i.e. formation of related words of a word-family from phonemically different roots. As a rule in the word-families of this type we are likely to encounter etymologically different words, e.g. the words brother and mouth are of Germanic origin, whereas fraternal and oral can be easily traced back to Latin. We frequently find synonymic pairs of the type fatherly— paternal, brotherly—fraternal.
Semantic and phonemic identity of affixational morphemes can be observed in the lexical groups of the type darkness, cleverness, calmness, etc.; teacher, reader, writer, etc. In such word-groups as, e.g. teacher, musician, etc., only semantic similarity of derivational affixes is observed. As derivational affixes impart to the words a certain generalised meaning, we may single out lexical groups denoting the agent, the doer of the action (Nomina Agenti)—teacher, reader, etc. or lexical groups denoting actions (Nomina Acti)—movement, transformation, etc. and others.

В§ 52. Summary and Conclusions

1. Paradigmatic (or selectional) and syntagmatic (or combinatory) axes of linguistic structure represent the way vocabulary is organised.
Syntagmatic relations define the word-meaning in the flow of speech in various contexts.
Paradigmatic relations define the word-meaning through its interrelation with other members within one of the subgroups of vocabulary units.
2. On the syntagmatic axis the word-meaning is dependent on different types of contexts. Linguistic context is the minimal stretch of speech necessary to determine individual meanings.
3. Linguistic (verbal) contexts comprise lexical and grammatical contexts and are opposed to extra-linguistic (non-verbal) contexts. In extra-linguistic contexts the meaning of the word is determined not only by linguistic factors but also by the actual speech situation in which the word is used.
4. The semantic structure of polysemantic words is not homogeneous as far as the status of individual meanings is concerned. A certain meaning (or meanings) is representative of the word taken in isolation, others are perceived only in various contexts.
5. Classification of vocabulary into thematic groups is based on common contextual associations. Contextual associations are formed as a result of regular co-occurrence of words in similar, repeatedly used contexts within the framework of sentences.
6. The main criterion underlying semantic classification of vocabulary items on the paradigmatic axis is the type of meaning relationship between words.
The criterion of common concept serves to classify words into semantic fields and lexico-semantic groups.
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Semantic relationship of inclusion is the main feature of hyponymic hierarchical structure Semantic similarity and semantic contrast is the type of relationship which underlies the classification of lexical items into synonymic and antonymic series.
7. Synonymy and antonymy are correlative and sometimes overlapping notions. Synonymous relationship of the denotational meaning is in many cases combined with the difference in the connotational (mainly stylistic) component.
8. It is suggested that the term synonyms should be used to describe words different in sound-form but similar in their denotational meaning (or meanings) and interchangeable at least in some contexts.
The term antРѕnСѓms is to be applied to words different in sound-form characterised by different types of semantic contrast of the denotational meaning and interchangeable at least in some contexts.