Diachronically

A story, a science fiction film, or, in fact, a scientific theory, can thus be positioned at a higher and later turning of the spiral, diachronically, but synchronically it can be a performance of a pattern or theme.

In particular, risks can pile up not only synchronically, as in multi premise deductions, but also diachronically, when a subject extends her knowledge by competent deduction from just one premise.

Further, by presenting lexical information diachronically, it displays the stability of the particular words, spellings, usages, idioms, etc., and thus cumulatively the overall stability of the language or variety in general.