lymphocyte vs white cell

lymphocyte and white cell both are nouns.

Word	Noun	Adjective	Verb	Adverb
lymphocyte	Yes	No	No	No
white cell	Yes	No	No	No

As nouns, white cell is a hypernym of lymphocyte; that is, white cell is a word with a broader meaning than lymphocyte:

lymphocyte: an agranulocytic leukocyte that normally makes up a quarter of the white blood cell count but increases in the presence of infection
white cell: blood cells that engulf and digest bacteria and fungi; an important part of the body's defense system

Other hypernyms of lymphocyte include leucocyte, leukocyte, WBC, white blood cell, white blood corpuscle, white corpuscle.

lymphocyte (noun)	white cell (noun)
an agranulocytic leukocyte that normally makes up a quarter of the white blood cell count but increases in the presence of infection	blood cells that engulf and digest bacteria and fungi; an important part of the body's defense system