Things that are indistinguishable are so similar that you cannot see any difference between them. The usual pattern is indistinguishable from: this copy is indistinguishable from the real one.

Things that are indistinguishable難以分辨的東西 are so similar如此相似 that you cannot see以至於你看不出 any difference between them它們之間的任何差異。The usual pattern最常見的用法 is indistinguishable from就是「indistinguishable from」：this copy這個複製品 is indistinguishable from the real one跟真品分不出來。

You will also hear it about voices, taste, and even ideas. It is a careful, slightly formal word.

You will also hear it你也會聽到這個字用 about voices, taste, and even ideas在聲音、味道，甚至想法上。It它 is是 a careful, slightly formal word一個謹慎、稍微正式的詞。

Everyday talk: “you can’t tell them apart” or “they look the same.” Though actually, people also use it when two things have become mixed in the mind — two singers, two brands, two days — not only when they look identical under a light.

Everyday talk日常說法就是「you can't tell them apart」或「they look the same」。Though actually不過其實，people also use it大家也會用這個字 when two things have become mixed in the mind當兩件東西在腦海裡混在一起的時候——two singers, two brands, two days兩個歌手、兩個品牌、兩天——not only when they look identical under a light不只是在燈光下看起來一模一樣的時候而已。

The describing word is the one you will meet; using it as a noun is rare.

The describing word這個形容詞 is the one you will meet是你會遇到的；using it as a noun把它當名詞用 is rare很少見。