-logy
-logy is a suffix in the English language, used with words originally adapted from Ancient Greek ending in -λογία (-logía). The earliest English examples were anglicizations of the French -logie, which was in turn inherited from the Latin -logia. The suffix became productive in English from the 18th century, allowing the formation of new terms with no Latin or Greek precedent. The English suffix has two separate main senses, reflecting two sources of the -λογία suffix in Greek:

a combining form used in the names of school or bodies of knowledge, e.g., theology (loaned from Latin in the 14th century) or sociology. In words of the type theology, the suffix is derived originally from -λογ- (-log-) (a variant of -λεγ-, -leg-), from the Greek verb λέγειν (legein, 'to speak').