For example, there are positions in which complementizers are obligatory, optional or impossible, and these positions vary across languages and times.
The items below are presented as optional ways of writing the same word or expression, some with the apostrophe/stop, others without.
Evidently, an interpretation of a derivation is determined by its action on the optional axioms.
These devices can be combined with optional clausestructure variations, which reflect the fact that word order also encodes discourse status.
This was accomplished by defining optional matrix columns.
Up until 1945, the optional referendum represented an efficient veto point for groups opposing the welfare state to dilute state-interventionist social policies.
Two further modules have to be chosen from the following optional modules: advanced statistical methods, clinical trials, qualitative research methods, and advanced health economics.
A postgraduate diploma option can be obtained after completion of the core and optional modules or a master's degree after an additional research project dissertation.
