transitive verb

1. to hold or keep in possession
2. to keep in a fixed state or condition
3. to continue to have or hold in to retain heat
4. to continue to practice, use, etc.
5. to keep in mind
6. to hire, or arrange in advance for the services of, by paying a retainer

Etymology: ME reteynen < OFr retenir < LL *retenere, for L retinere < re-, back + tenere, to hold: see thin