"lower boundary" meaning in English

{
  "forms": [
    {
      "form": "lower boundaries",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "lower boundary (plural lower boundaries)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Geology",
          "orig": "en:Geology",
          "parents": [
            "Earth sciences",
            "Sciences",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "The most ancient time encompassed by a given geological period."
      ],
      "id": "en-lower_boundary-en-noun-ftZvNtvK",
      "links": [
        [
          "geology",
          "geology"
        ]
      ],
      "raw_glosses": [
        "(geology) The most ancient time encompassed by a given geological period."
      ],
      "topics": [
        "geography",
        "geology",
        "natural-sciences"
      ]
    },
    {
      "categories": [
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Linguistics",
          "orig": "en:Linguistics",
          "parents": [
            "Language",
            "Social sciences",
            "Communication",
            "Sciences",
            "Society",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        },
        {
          "_dis": "18 82",
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w+disamb"
        },
        {
          "_dis": "16 84",
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w+disamb"
        },
        {
          "_dis": "16 84",
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w+disamb"
        }
      ],
      "glosses": [
        "The most recent time encompassed by a given period of time."
      ],
      "id": "en-lower_boundary-en-noun-b2s064ZI",
      "links": [
        [
          "linguistics",
          "linguistics"
        ]
      ],
      "raw_glosses": [
        "(linguistics) The most recent time encompassed by a given period of time."
      ],
      "related": [
        {
          "_dis1": "25 75",
          "word": "upper boundary"
        }
      ],
      "topics": [
        "human-sciences",
        "linguistics",
        "sciences"
      ]
    }
  ],
  "word": "lower boundary"
}

{
  "categories": [
    "English countable nouns",
    "English entries with incorrect language header",
    "English lemmas",
    "English multiword terms",
    "English nouns",
    "Pages with 1 entry",
    "Pages with entries"
  ],
  "forms": [
    {
      "form": "lower boundaries",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "lower boundary (plural lower boundaries)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "upper boundary"
    }
  ],
  "senses": [
    {
      "categories": [
        "en:Geology"
      ],
      "glosses": [
        "The most ancient time encompassed by a given geological period."
      ],
      "links": [
        [
          "geology",
          "geology"
        ]
      ],
      "raw_glosses": [
        "(geology) The most ancient time encompassed by a given geological period."
      ],
      "topics": [
        "geography",
        "geology",
        "natural-sciences"
      ]
    },
    {
      "categories": [
        "en:Linguistics"
      ],
      "glosses": [
        "The most recent time encompassed by a given period of time."
      ],
      "links": [
        [
          "linguistics",
          "linguistics"
        ]
      ],
      "raw_glosses": [
        "(linguistics) The most recent time encompassed by a given period of time."
      ],
      "topics": [
        "human-sciences",
        "linguistics",
        "sciences"
      ]
    }
  ],
  "word": "lower boundary"
}