"proper motion" meaning in English

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      "expansion": "Latin proprius",
      "name": "der"
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  ],
  "etymology_text": "proper (in the sense of \"its own\") + motion; from Latin proprius.",
  "forms": [
    {
      "form": "proper motions",
      "tags": [
        "plural"
      ]
    }
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      "expansion": "proper motion (plural proper motions)",
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  "lang_code": "en",
  "pos": "noun",
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      "glosses": [
        "The change in apparent position of a celestial body due to that body's velocity relative to the Sun."
      ],
      "id": "en-proper_motion-en-noun-Q~0qTrek",
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      "raw_glosses": [
        "(astronomy) The change in apparent position of a celestial body due to that body's velocity relative to the Sun."
      ],
      "related": [
        {
          "word": "improper motion"
        },
        {
          "word": "radial velocity"
        },
        {
          "word": "peculiar motion"
        },
        {
          "word": "peculiar velocity"
        }
      ],
      "topics": [
        "astronomy",
        "natural-sciences"
      ],
      "wikipedia": [
        "proper motion"
      ]
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  "word": "proper motion"
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    {
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        "2": "la",
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      "expansion": "Latin proprius",
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    }
  ],
  "etymology_text": "proper (in the sense of \"its own\") + motion; from Latin proprius.",
  "forms": [
    {
      "form": "proper motions",
      "tags": [
        "plural"
      ]
    }
  ],
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      "expansion": "proper motion (plural proper motions)",
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  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "improper motion"
    },
    {
      "word": "radial velocity"
    },
    {
      "word": "peculiar motion"
    },
    {
      "word": "peculiar velocity"
    }
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        "The change in apparent position of a celestial body due to that body's velocity relative to the Sun."
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        "(astronomy) The change in apparent position of a celestial body due to that body's velocity relative to the Sun."
      ],
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        "astronomy",
        "natural-sciences"
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      "wikipedia": [
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