"keystone" meaning in English

{
  "categories": [],
  "etymology_templates": [
    {
      "args": {
        "1": "key",
        "2": "stone"
      },
      "expansion": "key + stone",
      "name": "compound"
    }
  ],
  "etymology_text": "key + stone",
  "forms": [
    {
      "form": "keystone",
      "tags": [
        "singular"
      ]
    },
    {
      "form": "keystones",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "expansion": "[POS TABLE]",
      "name": "noun"
    }
  ],
  "hyphenation": "key‧stone",
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [],
      "examples": [
        {
          "text": "Trust is the keystone of any strong relationship."
        }
      ],
      "glosses": [
        "A keystone is the most important part of something, on which everything else depends."
      ],
      "id": "simple-keystone-en-noun-~UxeTQGS",
      "raw_tags": [
        "countable"
      ]
    },
    {
      "categories": [
        {
          "kind": "other",
          "name": "Attributive modifiers",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "text": "Education is the keystone policy of the new government."
        },
        {
          "text": "Keystone species play a critical role in maintaining the structure of an ecosystem."
        }
      ],
      "glosses": [
        "A keystone part is the most important or foundational part of a system or plan."
      ],
      "id": "simple-keystone-en-noun-1M4YccFp",
      "raw_tags": [
        "usually before a noun"
      ]
    },
    {
      "categories": [],
      "examples": [
        {
          "text": "The old bridge's arch was held up by a single keystone."
        }
      ],
      "glosses": [
        "A keystone is the central stone at the top of an arch that holds the other stones in place."
      ],
      "id": "simple-keystone-en-noun-iLsVmlVR",
      "raw_tags": [
        "countable"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ˈkiːstoʊn/"
    }
  ],
  "word": "keystone"
}

{
  "categories": [
    "Compound terms"
  ],
  "etymology_templates": [
    {
      "args": {
        "1": "key",
        "2": "stone"
      },
      "expansion": "key + stone",
      "name": "compound"
    }
  ],
  "etymology_text": "key + stone",
  "forms": [
    {
      "form": "keystone",
      "tags": [
        "singular"
      ]
    },
    {
      "form": "keystones",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "expansion": "[POS TABLE]",
      "name": "noun"
    }
  ],
  "hyphenation": "key‧stone",
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "Countable nouns"
      ],
      "examples": [
        {
          "text": "Trust is the keystone of any strong relationship."
        }
      ],
      "glosses": [
        "A keystone is the most important part of something, on which everything else depends."
      ],
      "raw_tags": [
        "countable"
      ]
    },
    {
      "categories": [
        "Attributive modifiers"
      ],
      "examples": [
        {
          "text": "Education is the keystone policy of the new government."
        },
        {
          "text": "Keystone species play a critical role in maintaining the structure of an ecosystem."
        }
      ],
      "glosses": [
        "A keystone part is the most important or foundational part of a system or plan."
      ],
      "raw_tags": [
        "usually before a noun"
      ]
    },
    {
      "categories": [
        "Countable nouns"
      ],
      "examples": [
        {
          "text": "The old bridge's arch was held up by a single keystone."
        }
      ],
      "glosses": [
        "A keystone is the central stone at the top of an arch that holds the other stones in place."
      ],
      "raw_tags": [
        "countable"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ˈkiːstoʊn/"
    }
  ],
  "word": "keystone"
}