Constructions C1 and C2 may be similar in structural and/or semantic features. Then it may be helpful to provide a section which summarizes their commonalities and contrasts their differences. As an example, think of the English constructions ‘N is V-ing’ and ‘N is going to V’, or of ‘N1 of N2’ and ‘N2's N1’. Such a systematic comparison may be accompanied by pairs of examples illustrating both constructions. The question is how this fits in the systematic subdivision of a descriptive grammar.
- The constructions to be compared are functionally similar. The comparison then takes place in the onomasiological grammar. For instance, X belongs to Y and X is Y's are two predications of belonging. They are naturally compared in the chapter on possession, subsection on predication of belonging.
- The constructions to be compared are structurally similar. The comparison then takes place in the semasiological grammar.
- For instance, C1 and C2 only differ in the occupation of a slot by a different member of a paradigm. Nominal groups differing only in one having the definite article where the other has the indefinite article are an example. The comparison may be in the section on the determined nominal group.
- Likewise, C2 forms a syntactic paradigm with C1; for instance, C1 is basic, C2 is derived. An active construction and the corresponding passive construction are an example. The comparison could be in the section devoted to the derived construction.
Instead of a subsection comparing C1 and C2, the two sections describing C1 and C2 may be structured in parallel fashion, using analogous examples to the extent appropriate. Then a simple mutual cross-reference may suffice.