( ( eclipse ( ( A ( lunar eclipse ) ) ( occurs ( when ( ( the Moon ) ( passes ( into ( ( the ( Earth 's ) ) shadow ) ) ) ) ) ) ) ) . )
(ROOT (S (VP (VB eclipse) (SBAR (S (NP (DT A) (NN lunar) (NN eclipse)) (VP (VBZ occurs) (SBAR (WHADVP (WRB when)) (S (NP (DT the) (NNP Moon)) (VP (VBZ passes) (PP (IN into) (NP (NP (DT the) (NN Earth) (POS 's)) (NN shadow)))))))))) (. .)))
eclipse A lunar eclipse occurs when the Moon passes into the Earth's shadow.
(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.