{
  "chapter_id": "04",
  "slug": "articles",
  "title": "Articles",
  "time_range_sec": [983, 1134],
  "summary": "Definite (el/la/los/las) and indefinite (un/una/unos/unas) articles, gender/number agreement, and common exceptions like el problema, el día, la mano, la foto.",
  "suggested_grammar_note_id": null,
  "rules": [
    {
      "title": "Gender by ending (defaults)",
      "bullets": [
        "Nouns ending in -o tend to be masculine (el libro).",
        "Nouns ending in -a tend to be feminine (la piscina).",
        "Nouns ending in -d are usually feminine (la ciudad).",
        "Nouns ending in -ción are feminine (la acción)."
      ]
    },
    {
      "title": "Common exceptions",
      "bullets": [
        "Greek-origin -ma nouns are masculine: el problema, el programa, el tema.",
        "el día and el agua are masculine articles (agua takes el for euphony).",
        "la foto, la moto are feminine (short for fotografía, motocicleta).",
        "la clase, la carne are feminine despite ending in -e."
      ]
    },
    {
      "title": "un vs uno",
      "bullets": [
        "un libro = a book.",
        "uno = one (number, stands alone, not before a masculine noun).",
        "una libro is wrong — agreement must match the noun's gender."
      ]
    }
  ],
  "examples": [
    {"es": "el libro", "en": "the book", "tags": ["definite", "masculine"]},
    {"es": "la piscina", "en": "the pool", "tags": ["definite", "feminine"]},
    {"es": "los libros", "en": "the books", "tags": ["plural"]},
    {"es": "las piscinas", "en": "the pools", "tags": ["plural"]},
    {"es": "un libro", "en": "a book", "tags": ["indefinite"]},
    {"es": "una piscina", "en": "a pool", "tags": ["indefinite"]},
    {"es": "unos libros", "en": "some books", "tags": ["indefinite", "plural"]},
    {"es": "unas piscinas", "en": "some pools", "tags": ["indefinite", "plural"]},
    {"es": "la clase", "en": "the class", "tags": ["exception"]},
    {"es": "la ciudad", "en": "the city", "tags": ["exception", "-d"]},
    {"es": "el problema", "en": "the problem", "tags": ["exception", "-ma"]},
    {"es": "el día", "en": "the day", "tags": ["exception"]},
    {"es": "el agua", "en": "the water", "tags": ["exception", "stressed-a"]},
    {"es": "la foto", "en": "the photo", "tags": ["exception", "abbreviation"]}
  ],
  "vocab": [
    {"es": "libro", "en": "book", "pos": "noun"},
    {"es": "piscina", "en": "pool", "pos": "noun"},
    {"es": "clase", "en": "class", "pos": "noun"},
    {"es": "carne", "en": "meat", "pos": "noun"},
    {"es": "ciudad", "en": "city", "pos": "noun"},
    {"es": "universidad", "en": "university", "pos": "noun"},
    {"es": "acción", "en": "action", "pos": "noun"},
    {"es": "problema", "en": "problem", "pos": "noun"},
    {"es": "programa", "en": "program", "pos": "noun"},
    {"es": "día", "en": "day", "pos": "noun"},
    {"es": "agua", "en": "water", "pos": "noun"},
    {"es": "foto", "en": "photo", "pos": "noun"}
  ],
  "conjugation_tables": [],
  "exercises": [
    {"sentence": "_____ libro está en la mesa.", "correct": "El", "distractor": "La", "explanation": "libro ends in -o → masculine → el."},
    {"sentence": "Voy a _____ piscina.", "correct": "la", "distractor": "el", "explanation": "piscina ends in -a → feminine → la."},
    {"sentence": "_____ problema es difícil.", "correct": "El", "distractor": "La", "explanation": "Greek-origin -ma noun → masculine: el problema."},
    {"sentence": "Tengo _____ libro nuevo.", "correct": "un", "distractor": "uno", "explanation": "Before a masculine noun use un, not uno."},
    {"sentence": "_____ ciudad es grande.", "correct": "La", "distractor": "El", "explanation": "Nouns ending in -d are usually feminine."},
    {"sentence": "Bebo _____ agua fría.", "correct": "el", "distractor": "la", "explanation": "agua takes el in the singular (stressed initial a-) even though it's feminine."},
    {"sentence": "Quiero ver _____ foto.", "correct": "la", "distractor": "el", "explanation": "foto is short for fotografía → feminine."}
  ],
  "caveats": null
}