( <br /> ( ( A balance ) ( ( is ( ( ( a kind ) ( of scale ) ) ( which ( compares ( ( ( ( ( ( the masses ) ( of ( two objects ) ) ) , ) ( ( usually one ) ( with ( ( a ( known mass ) ) ( -LRB- ( ( the standard ) -RRB- ) ) ) ) ) ) and ) ( one ( with ( an ( unknown mass ) ) ) ) ) ) ) ) ) . ) ) )
(ROOT (S (ADVP (RB <br />)) (NP (DT A) (NN balance)) (VP (VBZ is) (NP (NP (DT a) (NN kind)) (PP (IN of) (NP (NN scale))) (SBAR (WHNP (WDT which)) (S (VP (VBZ compares) (NP (NP (NP (DT the) (NNS masses)) (PP (IN of) (NP (CD two) (NNS objects)))) (, ,) (NP (NP (RB usually) (CD one)) (PP (IN with) (NP (NP (DT a) (JJ known) (NN mass)) (PRN (-LRB- -LRB-) (NP (DT the) (NN standard)) (-RRB- -RRB-))))) (CC and) (NP (NP (CD one)) (PP (IN with) (NP (DT an) (JJ unknown) (NN mass)))))))))) (. .)))
<br />A balance is a kind of scale which compares the masses of two objects, usually one with a known mass (the standard) and one with an unknown mass.
(ROOT (S (NP (DT A) (NN student)) (VP (MD should) (VP (VB use) (NP (DT a) (NN balance) (S (VP (TO to) (VP (VB compare) (NP (NP (DT the) (NNS masses)) (PP (IN of) (NP (CD two) (JJ small) (NNS rocks)))))))))) (. .)))