lymphocyte vs leucocyte

lymphocyte and leucocyte both are nouns.

Word	Noun	Adjective	Verb	Adverb
lymphocyte	Yes	No	No	No
leucocyte	Yes	No	No	No

As nouns, leucocyte is a hypernym of lymphocyte; that is, leucocyte 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
leucocyte: blood cells that engulf and digest bacteria and fungi; an important part of the body's defense system

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

lymphocyte (noun)	leucocyte (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