Greek diakonia — "service, ministry, attendance on another, especially at table." The English "deacon" (Acts 6, 1 Timothy 3) comes straight from it. Biblical service is not the heroic public ministry people want, but the unglamorous daily readiness to meet another's need — holding the door, washing the dishes, making the coffee, babysitting, taking a meal to the sick, cleaning the toilet nobody else wants to touch. Jesus defines greatness by it: "Whoever would be great among you must be your servant" (Matthew 20:26).
Service as a spiritual discipline is deliberate, chosen service — especially of those who cannot repay you, and service no one will see. Jesus' foot-washing in John 13 is the template. He took off His outer garment, wrapped Himself in a towel, and did the slave's job none of the disciples was willing to do. "If I then, your Lord and Teacher, have washed your feet, you also ought to wash one another's feet" (John 13:14). The discipline of service pulls out pride by the root — because the self-important cannot bend down to help. It heals envy — because you are no longer competing for status, you are doing what nobody else wants to do. It cures entitlement — because expecting service is the opposite of offering it. Practical applications: volunteer for the behind-the-scenes jobs at church (setup, cleanup, nursery); serve your spouse in ways they do not notice; do the thing you are embarrassed to be seen doing; serve strangers with no expectation of thanks. Jesus came "not to be served but to serve and to give his life as a ransom for many" (Mark 10:45). The disciple takes the same towel.