Lethargic vs. Somnolent: What's the Difference?

Lethargic and Somnolent Definitions

Of, causing, or characterized by lethargy.

Drowsy; sleepy.

Sluggish, slow

Inducing or tending to induce sleep; soporific.

Indifferent, apathetic

Drowsy or sleepy.

Pertaining to, affected with, or resembling, lethargy; morbidly drowsy; dull; heavy.

(dated) Causing literal or figurative sleepiness.

Deficient in alertness or activity;

Bullfrogs became lethargic with the first cold nights

Sleepy; drowsy; inclined to sleep.

He had no eye for such phenomena, because he had a somnolent want of interest in them.

Inclined to or marked by drowsiness;

Slumberous (or slumbrous) eyes

`slumbery' is archaic

The sound had a a somnolent effect