This root form (lemma) is used in 2 different forms in the NT: ἰοῦ (GMS), ἰὸς (NMS).
It is glossed in 3 different ways: ‘of poison’, ‘poison’, ‘rust’.
OET ROM 3:13 Greek word=ἰὸς (ios) Morphology=NMS English gloss=‘poison’ SR GNT ROM 3:13 word 10
OET JAM 3:8 Greek word=ἰοῦ (iou) Morphology=GMS English gloss=‘of poison’ SR GNT JAM 3:8 word 14
OET JAM 5:3 Greek word=ἰὸς (ios) Morphology=NMS English gloss=‘rust’ SR GNT JAM 5:3 word 11