Why are prefixes and suffixes divided according to different criteria?

Prefixes and suffixes are categorized by different criteria due to three key aspects. Functionally, prefixes focus on semantic adjustment, altering root meanings while keeping word classes stable (e.g., “un - ” negates, “pre - ” adds time info). Suffixes prioritize part - of - speech conversion, changing word classes with auxiliary meanings (e.g., “-er” turns verbs to nouns, “-ful” shifts nouns to adjectives). Evolutionarily, prefixes stem from ancient function words (prepositions/adverbs like Latin “prae”), retaining “semantic modification” roles. Suffixes evolve from content words, losing independent meanings to become “part - of - speech markers” (e.g., “-er” from a noun meaning “person” to a verb - to - noun converter). Grammatically and semantically, words with prefixes keep their part - of - speech, so they're classified by “semantic types”. Words with suffixes change part - of - speech, requiring “part - of - speech + auxiliary meaning” criteria. Prefix semantics are freer (negation, time), while suffix semantics are restricted by part - of - speech (noun suffixes relate to “people/concepts”, adjective suffixes to “qualities”). These differences make distinct criteria necessary.