The police officer was promoted to subordinate officer for outstanding performance.

subordinate 由前缀 sub-（表示"在...之下"）和词根 ordinate（排列、顺序）组成，意思是"下级的、从属的"。 officer 指"官员、警官"，特指担任特定职务的人。 subordinate officer 指"下级警官"，即警衔较低的警官职位。