Insidious vs. Invidious

Insidious vs. Invidious “Insidious” vs. “Invidious” “Insidious” vs. “Invidious” By Mark Nichol What’s the difference between insidious and invidious, and what about perfidious and pernicious, for that matter? None of the four words is synonymous with any of the others, though your connotation radar may correctly sense that they all have unpleasant associations. Insidious, which derives from the Latin word for “ambush” (the second syllable is cognate with sit), means “treacherous” or “seductive,” with an additional connotation of “subtle,” in the sense of a gradual, cumulative effect. (This, unlike the other meanings, is neutral, but the word is rarely used except in a negative sense.) For example, in medical terminology, an insidious disease is one that remains hidden until it is well established. The noun form is insidiousness, and the adverbial form is insidiously.

Insidious vs. Invidious