The fatted calf (ton moschon ton siteuton). The calf the fatted one. Siteuton is the verbal adjective of sileuō, to feed with wheat (sitos). The calf was kept fat for festive occasions, possibly in the hope of the son’s return.
Kill (thusate). Not as a sacrifice, but for the feast.
Make merry (euphranthōmen). First aorist passive subjunctive (volitive). From euphrainō, an old verb from eu (well) and phrēn (mind).