reservist [reservists](a soldier who is assigned as reserved; after training, no longer in full active duty) noun [UK: rɪ.ˈzɜː.vɪst] [US: rə.ˈzɝː.vəst]
預備役 /yùbèiyì/ noun
reserve [reserves](military: body of troops in the rear of an army) noun [UK: rɪ.ˈzɜːv] [US: rə.ˈzɝːv]