noun
1.
the performance of military duty in wartime and especially in a combat zone
saw a year's service in Vietnam
Synonyms: action, combat
Related Word: active duty, duty; fighting
2.
Synonyms: favor 4, courtesy, dispensation, indulgence, kindness
3.
Synonyms: rite 2, ceremonial, ceremony, formality, liturgy, observance, ritual
4.
Synonyms: use 3, account, advantage, applicability, appropriateness, avail, fitness, relevance, serviceability, usefulness