def get_def_class(word):
    """
    get_def_class()

    Purpose: Checks for a definitive classification at the word level.

    @param word. A string
    @return      1 if the word is a test term,
                 2 if the word is a problem term,
                 3 if the word is a treatment term,
                 0 otherwise.
    >>> get_def_class('eval')
    1
    >>> get_def_class('rate')
    1
    >>> get_def_class('tox')
    1
    >>> get_def_class('swelling')
    2
    >>> get_def_class('mass')
    2
    >>> get_def_class('broken')
    2
    >>> get_def_class('therapy')
    3
    >>> get_def_class('vaccine')
    3
    >>> get_def_class('treatment')
    3
    >>> get_def_class('unrelated')
    0
    """
    test_terms = {
        "eval", "evaluation", "evaluations",
        "sat", "sats", "saturation",
        "exam", "exams",
        "rate", "rates",
        "test", "tests",
        "xray", "xrays",
        "screen", "screens",
        "level", "levels",
        "tox"
    }
    problem_terms = {
        "swelling",
        "wound", "wounds",
        "symptom", "symptoms",
        "shifts", "failure",
        "insufficiency", "insufficiencies",
        "mass", "masses",
        "aneurysm", "aneurysms",
        "ulcer", "ulcers",
        "trama", "cancer",
        "disease", "diseased",
        "bacterial", "viral",
        "syndrome", "syndromes",
        "pain", "pains"
                "burns", "burned",
        "broken", "fractured"
    }
    treatment_terms = {
        "therapy",
        "replacement",
        "anesthesia",
        "supplement", "supplemental",
        "vaccine", "vaccines"
                   "dose", "doses",
        "shot", "shots",
        "medication", "medicine",
        "treatment", "treatments"
    }
    if word.lower() in test_terms:
        return 1
    elif word.lower() in problem_terms:
        return 2
    elif word.lower() in treatment_terms:
        return 3
    return 0