-logical Also -logic.
Relating to a branch of knowledge or experience.
Many examples exist, of which a few are: astrological, biological, ecological, ideological, mineralogical, numerological, seismological, sociological, theological, and zoological.
Though -logical is the standard way of forming such adjectives, a few are also formed using -logic, such as hydrologic, morphologic, and physiologic. Adjectives sometimes exist in both spellings: geological and geologic; pharmacological and pharmacologic. In such cases, there is no clear distinction of sense, but the one ending in -logical is substantially more common.