deficient vs lacking

deficient and lacking both are adjectives.

Word	Noun	Adjective	Verb	Adverb
deficient	No	Yes	No	No
lacking	No	Yes	No	No

As adjectives, deficient and lacking are synonyms defined as:

Other synonyms of deficient include wanting.

deficient (adjective)	lacking (adjective)
of a quantity not able to fulfill a need or requirement	inadequate in amount or degree
inadequate in amount or degree	nonexistent
falling short of some prescribed norm