Greek word · G2728

κατιόομαι

katioomai

to corrode

A rare compound of kata ('down, thoroughly') and ioō ('to rust'): 'to be rusted over, corroded through, tarnished'. It occurs only here in the NT. Here it is perfect passive: a completed condition that still holds.

Appears once in the Greek New Testament. · Updated October 30, 2026

What it means

κατ-ιόω, -ῶ

(intensive of ἰόω; ἰός) [in LXX: Sirach 12:11 * ;]

to rust over; pass., become rusted over: James 5:3.†

(AS)

From G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922), via STEPBible.org (CC BY 4.0).

In depth

From the study of James 5:3

Range of meaning: A rare compound of kata ('down, thoroughly') and ioō ('to rust'): 'to be rusted over, corroded through, tarnished'. It occurs only here in the NT. Here it is perfect passive: a completed condition that still holds.
Against the English: 'Corroded' (BSB, WEB, ESV, NIV) and 'rusted' (NASB) are fair. KJV 'cankered' meant 'corroded, eaten away' in 1611, but modern readers hear disease. YLT 'rotted' carries over the rot language of v.2.
How it drifted: Not drift in the word itself. Modern readers may be puzzled because gold does not rust and conclude the image is naive science. The impossibility is the point.
Used elsewhere in the period: Sirach 29:10 (LXX) uses the simple verb in a very close thought: 'Lose your silver for a brother or friend, and do not let it rust (ioōthētō) under a stone to be lost.' Sirach 29:11 goes on: 'Lay up your treasure according to the commandments of the Most High.' The Letter of Jeremiah (Baruch 6) mocks gold and silver idols that cannot protect themselves from rust (ios). A fragment of the Greek poet Pindar calls gold 'child of Zeus' that 'neither moth nor worm devours', which reflects the common belief that gold does not decay.

Where it appears

James · 1

James 5:3 κατίωται have corroded

Your gold and silver are corroded. Their corrosion will testify against you and consume your flesh like fire. You have hoarded treasure in the last days.

Here: 'Has become thoroughly rusted/tarnished'. The verb is singular because gold and silver are treated as one hoard. It is in the perfect tense, which describes a state already reached: from God's point of view the decay is already done. The prefix kata- adds 'all the way through'.

Word data: STEPBible.org (CC BY 4.0), main text only.