( ( ( ( An eclipse ) ( of ( the Moon ) ) ) ( -LRB- ( ( lunar eclipse ) -RRB- ) ) ) ( ( is ( when ( ( ( the ( Earth 's ) ) shadow ) ( falls ( on ( the Moon ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NP (DT An) (NN eclipse)) (PP (IN of) (NP (DT the) (NNP Moon)))) (PRN (-LRB- -LRB-) (NP (NN lunar) (NN eclipse)) (-RRB- -RRB-))) (VP (VBZ is) (SBAR (WHADVP (WRB when)) (S (NP (NP (DT the) (NN Earth) (POS 's)) (NN shadow)) (VP (VBZ falls) (PP (IN on) (NP (DT the) (NNP Moon))))))) (. .)))
An eclipse of the Moon (lunar eclipse) is when the Earth's shadow falls on the Moon.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NP (NN earth) (POS 's)) (NN shadow)) (VP (VBZ falls) (PP (IN on) (NP (DT the) (NN moon)))))) (, ,) (NP (DT the) (NN shadow)) (VP (VBZ causes) (NP (DT a) (NN lunar) (NN eclipse))) (. .)))
When earth’s shadow falls on the moon, the shadow causes a lunar eclipse.