"which is which" meaning in English

{
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "phrase"
      },
      "expansion": "which is which",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "phrase",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "Used to indicate multiple things are difficult to tell apart"
      ],
      "id": "en-which_is_which-en-phrase-rm05z~BL",
      "raw_glosses": [
        "(informal, especially as a question) Used to indicate multiple things are difficult to tell apart"
      ],
      "raw_tags": [
        "as a question"
      ],
      "tags": [
        "especially",
        "informal"
      ]
    }
  ],
  "word": "which is which"
}

{
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "phrase"
      },
      "expansion": "which is which",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "phrase",
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English informal terms",
        "English lemmas",
        "English multiword terms",
        "English phrases",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "glosses": [
        "Used to indicate multiple things are difficult to tell apart"
      ],
      "raw_glosses": [
        "(informal, especially as a question) Used to indicate multiple things are difficult to tell apart"
      ],
      "raw_tags": [
        "as a question"
      ],
      "tags": [
        "especially",
        "informal"
      ]
    }
  ],
  "word": "which is which"
}