( ( The ( sunspot cycle ) ) ( ( is ( ( ( ( ( a variation ) ( over ( 11 ( ( -LRB- ( ( or 22 ) -RRB- ) ) years ) ) ) ) -RRB- ) ( of ( ( the number ) ( of ( ( sunspots and ) ( their position ) ) ) ) ) ) ( on ( ( the surface ) ( of ( the Sun ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN sunspot) (NN cycle)) (VP (VBZ is) (PP (PP (NP (NP (DT a) (NN variation)) (PP (IN over) (NP (ADJP (CD 11)) (PRN (-LRB- -LRB-) (NP (QP (CC or) (CD 22))) (-RRB- -RRB-)) (NNS years))) (-RRB- -RRB-)) (IN of) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NP (NNS sunspots)) (CC and) (NP (PRP$ their) (NN position)))))) (PP (IN on) (NP (NP (DT the) (NN surface)) (PP (IN of) (NP (DT the) (NNP Sun))))))) (. .)))
The sunspot cycle is a variation over 11 (or 22) years) of the number of sunspots and their position on the surface of the Sun.
(ROOT (S (NP (NNS Sunspots)) (VP (VBP occur) (PP (IN in) (NP (DT a) (CD 11) (NN year) (NN cycle)))) (. .)))