二相 is read as にそう (nisou) and means two-phase.
にそう
nisou
にこくかんそうごしゅぎ
bilateralism
はたち
20 years old
にりゅう
second-rate
にぶ
two parts
にじ
second
にじゅうよじかんせい
around-the-clock system
にき
two periods
にばん
にのつぎ
secondary
にごう
number two
によう
two flat things
ふたりづれ
party of two