( ( An organ ) ( ( is ( ( a structure ) ( that ( contains ( ( ( ( at least ) two ) ( different types ) ) ( of ( tissue ( ( functioning together ) ( for ( a ( common purpose ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT An) (NN organ)) (VP (VBZ is) (NP (NP (DT a) (NN structure)) (SBAR (WHNP (WDT that)) (S (VP (VBZ contains) (NP (NP (QP (IN at) (JJS least) (CD two)) (JJ different) (NNS types)) (PP (IN of) (NP (NP (NN tissue)) (VP (VBG functioning) (ADVP (RB together)) (PP (IN for) (NP (DT a) (JJ common) (NN purpose)))))))))))) (. .)))
An organ is a structure that contains at least two different types of tissue functioning together for a common purpose.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NP (JJ different) (NNS types)) (PP (IN of) (NP (NNS tissues)))) (VP (VBP work) (ADVP (RB together)) (S (VP (TO to) (VP (VB perform) (NP (DT a) (JJ unique) (NN function)))))))) (, ,) (NP (PRP they)) (VP (VBP form) (NP (NN organ))) (. .)))