A grammar usually organizes words into noun, verb, adjective, and other parts of speech according to what they mean and how they function. Because lexical items denote objects, events, states or attributes in the physical or mental world, a linguistic ontology serves not only as a bridge between lexis and semantics but also as an interface between linguistic knowledge and world knowledge. Linguistic studies have symbiotic associations with written languages or writing systems. Every language has lexis and grammar, but linguistic studies have been entirely unbalanced in favour of the former. Contemporary linguistics tend to strike a balance between lexical and grammatical studies. Scholars attempt to include lexis into grammatical studies and grammar into lexical studies. Most existing lexical semantic theories try to separate world knowledge from linguistic knowledge. Structural semantics focuses on paradigmatic relations between words, for example, synonymy, antonymy, hyponymy and other relevant sense relations.