def singularize(plural):
    """Convert plural word to its singular form.

    Args:
        plural: A word in its plural form.
    Returns:
        The word in its singular form.
    """
    if plural in UNCOUNTABLES:
        return plural
    for i in IRREGULAR:
        if i[1] == plural:
            return i[0]
    for i in SINGULARIZE_PATTERNS:
        if re.search(i[0], plural):
            return re.sub(i[0], i[1], plural)
    return plural
Convert plural word to its singular form.

    Args:
        plural: A word in its plural form.
    Returns:
        The word in its singular form.