ailing vs sickly

ailing and sickly both are adjectives.

Word	Noun	Adjective	Verb	Adverb
ailing	No	Yes	No	No
sickly	No	Yes	No	No

As adjectives, ailing and sickly are synonyms defined as:

Other synonyms of ailing include indisposed, peaked, poorly, seedy, under the weather, unwell.

ailing (adjective)	sickly (adjective)
somewhat ill or prone to illness	somewhat ill or prone to illness
	unhealthy looking