Even well-educated English native speakers regularly bungle the following two terms in spoken contexts:

1. “home in”: When “focusing” on something, English natives will often incorrectly assert they are “honing in on” [a thing], thus confounding “to hone” (to sharpen or whet) with the correct phrasing “home in on” (as in a heat-seeking missile). Interestingly, even extremely intelligent and well-read natives commit this error.
2. “phenomena” vs. “phenomenon”: For some reason English natives will habitually use the singular “phenomenon” when meaning to refer to the plural “phenomena”. And even when they deploy the plural correctly, you can often hear the cerebral gears turning during the slight pause the speaker inserts prior to enunciating the word.