Meaning of the Sanskrit Word: sapatnyah

  sapatnyah—of the co-wife    SB 4.8.14
  sapatnyah—spoken by her co-wife    SB 4.8.16
  sapatnyah—of the co-wife Krtadyuti    SB 6.14.42
  sapatnyah—of her co-wife (Suniti)    SB 4.8.10

Can't find any compound Sanskrit words containing sapatnyah.