"Ehrenstein illusion" meaning in English

{
  "etymology_text": "Studied by the German psychologist Walter Ehrenstein (1899–1961).",
  "forms": [
    {
      "form": "Ehrenstein illusions",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "Ehrenstein illusion (plural Ehrenstein illusions)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "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"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Optical illusions",
          "orig": "en:Optical illusions",
          "parents": [
            "Vision",
            "Senses",
            "Perception",
            "Body",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "An optical illusion in which the sides of a square placed inside a pattern of concentric circles take an apparent curved shape."
      ],
      "id": "en-Ehrenstein_illusion-en-noun-XfrtoTXw",
      "links": [
        [
          "optical illusion",
          "optical illusion"
        ],
        [
          "square",
          "square"
        ],
        [
          "concentric",
          "concentric"
        ],
        [
          "circle",
          "circle"
        ]
      ],
      "wikipedia": [
        "Ehrenstein illusion"
      ]
    }
  ],
  "word": "Ehrenstein illusion"
}

{
  "etymology_text": "Studied by the German psychologist Walter Ehrenstein (1899–1961).",
  "forms": [
    {
      "form": "Ehrenstein illusions",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "Ehrenstein illusion (plural Ehrenstein illusions)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English eponyms",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Optical illusions"
      ],
      "glosses": [
        "An optical illusion in which the sides of a square placed inside a pattern of concentric circles take an apparent curved shape."
      ],
      "links": [
        [
          "optical illusion",
          "optical illusion"
        ],
        [
          "square",
          "square"
        ],
        [
          "concentric",
          "concentric"
        ],
        [
          "circle",
          "circle"
        ]
      ],
      "wikipedia": [
        "Ehrenstein illusion"
      ]
    }
  ],
  "word": "Ehrenstein illusion"
}