Distinct vs. distinctive
Distinct = (1) easily distinguishable from other things, (2) discrete, or (3) easy to see. Distinctive = characteristic or serving to identify.
Demur vs. demure
Demur = (1) to object, or (2) to hesitate because of doubt. Demure = (1) modest and reserved, or (2) affectedly shy.
Drop off vs. drop-off (vs. dropoff)
Drop off: verb. Drop-off: noun.
Dwelled vs. dwelt
Dwelled is now more common in American English (a new development). Dwelt is still preferred everywhere else.
Disposed vs. predisposed
Disposed = (1) in a willing frame of mind toward something, (2) suitably placed or situated, or (3) having a tendency toward something. Predisposed = disposed in advance or inherently disposed.
Dribble vs. drivel
Drivel = senseless talk or content. Dribble = a small, unsteady stream.
Double-edged sword
a good thing that is also a bad thing.