Strong’s Greek
G4577 — seira
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
σειρά σιρός
seira — pronounced si-rah'
probably from 4951 through its congener eiro (to fasten; akin to 138); a chain (as binding or drawing):--chain. see GREEK for 4951 see GREEK for 138
1 occurrence in the KJV.
2 Peter 2:4
For if God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment;