forty winks vs light sleep

forty winks and light sleep both are nouns.

Word	Noun	Adjective	Verb	Adverb
forty winks	Yes	No	No	No
light sleep	Yes	No	No	No

As nouns, forty winks and light sleep are synonyms defined as:

forty winks and light sleep: sleeping for a short period of time (usually not in bed)

Other synonyms of forty winks include catnap, nap, short sleep, snooze.

forty winks (noun)	light sleep (noun)
sleeping for a short period of time (usually not in bed)	sleeping for a short period of time (usually not in bed)