Words may be in intersecting semantic classes. For example woman is in the class with property ‘female’, child is in the class ‘young’, and girl is in the intersecting class with the two properties ‘female’ and ‘young’.
Additionally, there are semantic relations between words and certain semantic categories may imply others. For example , the property ‘human’ implies ‘animate’.
Such relationship can be expressed by semantic features, similar to phonetic features. In this case the lexical entries for words such as father, girl and mare would have the following (incomplete) appearance.
woman father girl mare (to) stalk
+ female + male + female + female + motion
+ human + human + human - human + slow
- young + parent + young - young + purposeful
… … … + horseness …
Intersecting classes share the same features, such as the class of human females, which are marked ‘plus’ for the features human and female.
Additional fact, such as that ‘human’ implies ‘animate’, could be stated using redundancy rules on these features, for example.
[+ human] --> [+ animate]
The rule means that if any word contains the feature [+ human], it ‘automatically’ contains the feature [+ animate]. Therefore the feature [+ animate] need not be specifically mentioned in the lexical entry for father (or girl, professor, child); it can be inferred from the feature [+ human] by the redundancy rule.
Some semantic redundancy rules reveal ‘negative’ properties. For example, if something is ‘human’ it is not ‘abstract’; an activity that is ‘slow’ is not ‘fast’. Thus we could state:
[+ human] --> [-abstract]
[+ slow ] --> [- fast]