One of the primary differences between LMF and lemon is the handling of semantics. In LMF, similarly to other resources such as WordNet, there are a fixed set of senses, however in lemon the sense ties the lexical entry to an ontology. There are several reasons for this:
It is difficult to be certain of a fixed set of senses that fully capture all meanings of a word.
Words are frequently used with meanings beyond the dictionary set of senses (e.g., metonymic raising).
Different languages frequently divide senses in ways that are not natural in the other language (e.g., “river” in English and “rivière” and “fleuve” in French).
Senses have no inherent meaning, i.e., practical systems can only understand the meaning of a word by grounding it in some ontologically described formalism.
Ontology languages provide better modeling of semantics than a lexicon-based system can. Note that although lemon is intended to and likely to be used primarily with OWL, it is not necessary that the ontology system is OWL.
For these reasons the semantic modeling in lemon is more lightweight than that of LMF and so we have far fewer classes, as we do not wish to significantly duplicate the semantic modeling that should exist in the ontology.