"μάτην" meaning in Grec ancien

{
  "categories": [
    {
      "kind": "other",
      "name": "Adverbes en grec ancien",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Grec ancien",
      "orig": "grec ancien",
      "parents": [],
      "source": "w"
    }
  ],
  "etymology_texts": [
    "De μάτη, mátê (« vaine folie »)."
  ],
  "lang": "Grec ancien",
  "lang_code": "grc",
  "pos": "adv",
  "pos_title": "Adverbe",
  "raw_tags": [
    "μάτην, mátên"
  ],
  "related": [
    {
      "translation": "vain, futile, frivole",
      "word": "μάταιος"
    }
  ],
  "senses": [
    {
      "examples": [
        {
          "ref": "Eschyle, Prométhée enchaîné",
          "text": "εἶἑν, τί μέλλεις καὶ κατοικτίζῃ μάτην; τί τὸν θεοῖς ἔχθιστον οὐ στυγεῖς θεόν.",
          "translation": "Allons ! Que tardes-tu ? Vainement tu le prends en pitié, ce Dieu, en horreur aux Dieux."
        }
      ],
      "glosses": [
        "En vain, vainement."
      ],
      "id": "fr-μάτην-grc-adv-5GTbvsUz"
    }
  ],
  "word": "μάτην"
}

{
  "categories": [
    "Adverbes en grec ancien",
    "grec ancien"
  ],
  "etymology_texts": [
    "De μάτη, mátê (« vaine folie »)."
  ],
  "lang": "Grec ancien",
  "lang_code": "grc",
  "pos": "adv",
  "pos_title": "Adverbe",
  "raw_tags": [
    "μάτην, mátên"
  ],
  "related": [
    {
      "translation": "vain, futile, frivole",
      "word": "μάταιος"
    }
  ],
  "senses": [
    {
      "examples": [
        {
          "ref": "Eschyle, Prométhée enchaîné",
          "text": "εἶἑν, τί μέλλεις καὶ κατοικτίζῃ μάτην; τί τὸν θεοῖς ἔχθιστον οὐ στυγεῖς θεόν.",
          "translation": "Allons ! Que tardes-tu ? Vainement tu le prends en pitié, ce Dieu, en horreur aux Dieux."
        }
      ],
      "glosses": [
        "En vain, vainement."
      ]
    }
  ],
  "word": "μάτην"
}