def plural(n: int, def_one: str = '', def_many: str = 's') -> str:
    """
    Returns the plural form of a noun based on the number n.  By default, this
    function assumes a simple "s" can be used to make a noun plural.  If the
    plural word needs to change completely, the two options may be given in
    the optional arguments.  Example:
        plural(15, 'criterion', 'criteria')
    Returns 'criteria'.
    :param n: The number on which to determine if a plural form is needed or not.
    :param def_one: The string to return if the number is one.
    :param def_many: The string to return if the number is not one.
    :return: Returns the string to use for the plural form.
    """
    if n == 1:
        return def_one
    else:
        return def_many