Strong's G1398 — δουλεύω (verb)
douleuo (doul-yoo'-o) v.
1. to be a slave to
2. to be enslaved
3. (figuratively) to be subservient to
{literal or figurative, involuntary or voluntary}
[from G1401]
KJV: be in bondage, (do) serve(-ice) 
Root(s): G1401 
Hebrew root: δοῦλος
Occurrences: 25