( ( In fact ) ( , ( ( ( the definition ) ( of ( a ( eukaryotic cell ) ) ) ) ( ( is ( that ( it ( ( contains ( a nucleus ) ) ( while ( ( a ( prokaryotic cell ) ) ( is ( defined ( as ( not ( having ( a nucleus ) ) ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (NN fact))) (, ,) (NP (NP (DT the) (NN definition)) (PP (IN of) (NP (DT a) (JJ eukaryotic) (NN cell)))) (VP (VBZ is) (SBAR (IN that) (S (NP (PRP it)) (VP (VBZ contains) (NP (DT a) (NN nucleus)) (SBAR (IN while) (S (NP (DT a) (JJ prokaryotic) (NN cell)) (VP (VBZ is) (VP (VBN defined) (PP (IN as) (S (VP (RB not) (VBG having) (NP (DT a) (NN nucleus))))))))))))) (. .)))
In fact, the definition of a eukaryotic cell is that it contains a nucleus while a prokaryotic cell is defined as not having a nucleus.
(ROOT (S (NP (NP (DT The) (NN presence)) (PP (IN of) (NP (DT a) (NN nucleus)))) (VP (VBZ is) (NP (NP (DT the) (JJ main) (NN difference)) (PP (IN between) (NP (ADJP (JJ prokaryotic) (CC or) (JJ eukaryotic)) (NNS cells))))) (. .)))