Relationship of the two parts

In a systematic view, the onomasiological and semasiological description are complementary, symmetric and have equal weight in the overall description of a language. This equality is, however, limited, leading to an overweight of the semasiological description:

• The semasiological description takes the perspective of the hearer. It reflects passive knowledge of the language. Active knowledge of a language is never more comprehensive than passive knowledge; instead, it presupposes the latter.

Therefore the complete description of a construction is a task of the semasiological grammar. The onomasiological grammar refers to it.

The place of semanto-syntactic operations in the twofold description

There are at least to topical areas which are hard to accommodate consistently in a simple grammar, be it mixed, be it purely semasiological:

Coordination and negation are operations that apply at different grammatical levels, in different clause types and obey constraints of all sorts. The Alternative resulting therefrom is therefore: either one chapter on negation which describes all constructions involving negation; or for each grammatical construction, an appendix on its negation. And the same for coordination.

Since onomasiological grammar is devoted to linguistic operations whereas semasiological grammar is devoted to linguistic constructions, the alternative is resolved by treating such topical areas in both compartments of the description:

• A semasiological description separates all the negative and all the coordinative constructions, adding a subsection on negative and another on coordinative constructions to each of the relevant sections of the grammar.
• In the onomasiological grammar, there is one chapter on negation and one on coordination.

The place of grammaticalization in the twofold description

There are two places in the grammar where grammaticalization becomes part of the description:

• In the semasiological grammar, the function of the formatives constituting a construction is described. This may fruitfully incorporate a diachronic perspective and, thus, an account of the formative's origin by grammaticalization. For instance, the account of the prepositional phrase presents paradigms of prepositions of different degrees of grammaticalization. This is the place to mention that English of is grammaticalized from off.
• In the onomasiological grammar, a function in a given functional domain may be fulfilled in different degrees of explicitness. The constructions affording this may be connected by grammaticalization. For instance, a left-dislocated topic may be integrated into the clause as a fronted topic.
  Since grammaticalization involves condensation of grammatical structure, leading from relatively variable high-level syntactic or even discourse constructions to tightly-knit morphological constructions, these products are generally dealt with in different sections of a semasiological grammar. However, to the extent that the initial function is preserved, even in a diluted form, they can be treated together in a chapter of the onomasiological description.

Complexity is a structuring factor in both compartments of the grammatical description:

• In the semasiological grammar, each chapter devoted to a syntactic category consists of sections which climb the complexity hierarchy, from root and grammatical formative up to syntactic construction.
• In the onomasiological grammar, each chapter devoted to a concept or operation starts with the most explicit, lexical-syntactic constructions and moves complexity levels downwards down to the most grammaticalized constructions and formatives.

In this way, the onomasiological grammar also makes it explicit to which extent a given concept or operation is grammaticalized in the language.