劍橋詞典

[ 不可數(shù)或單數(shù)名詞：沒(méi)有復(fù)數(shù)形式的名詞 ]
abbreviation for patient controlled analgesia: a process in which patients suffering pain can control when and how they receive a drug to reduce their pain
自控式鎮(zhèn)痛（patient controlled analgesia的縮寫(xiě)）
[ 可數(shù)名詞：有復(fù)數(shù)形式的名詞 ]
abbreviation for posterior cerebral artery : a blood vessel that supplies blood to the back of the brain
大腦后動(dòng)脈（Posterior cerebral artery的縮寫(xiě)） 返回 PCA