You'll be able to remember that the prefix non- means “not” by using the phrase nonpoisonous, to get a compound which is nonpoisonous is “not” toxic. Meaning "not" in phrases taken from Latin and some other languages, non is really a independent phrase and is not hyphenated: non compos mentis, https://remingtonhnsxc.ourabilitywiki.com/9175760/the_definitive_guide_to_papiertaschen