"număr de masă" meaning in Roumain

{
  "categories": [
    {
      "kind": "other",
      "name": "Locutions nominales en roumain",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Roumain",
      "orig": "roumain",
      "parents": [],
      "source": "w"
    }
  ],
  "lang": "Roumain",
  "lang_code": "ro",
  "pos": "noun",
  "pos_title": "Locution nominale",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Lexique en roumain de la physique",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "Nombre de masse."
      ],
      "id": "fr-număr_de_masă-ro-noun-THTUcbKq",
      "tags": [
        "physical"
      ]
    }
  ],
  "tags": [
    "neuter"
  ],
  "word": "număr de masă"
}

{
  "categories": [
    "Locutions nominales en roumain",
    "roumain"
  ],
  "lang": "Roumain",
  "lang_code": "ro",
  "pos": "noun",
  "pos_title": "Locution nominale",
  "senses": [
    {
      "categories": [
        "Lexique en roumain de la physique"
      ],
      "glosses": [
        "Nombre de masse."
      ],
      "tags": [
        "physical"
      ]
    }
  ],
  "tags": [
    "neuter"
  ],
  "word": "număr de masă"
}