It's sometimes difficult to distinguish between Spanish and Portuguese.

distinguish 是动词，意思是"区分、辨别"。这个词由前缀 dis-（表示"分开"）和词根 stinguere（拉丁语，意为"分开、区分"）组成，字面意思是"将事物分开来看"，引申为"辨别、区分"的能力。