def plural_of (noun) :
    """Returns the plural from of the (english) `noun`.

    >>> print (plural_of ("house"))
    houses
    >>> print (plural_of ("address"))
    addresses
    >>> print (plural_of ("enemy"))
    enemies

    """
    result = noun
    if result.endswith ("s") :
        result += "es"
    elif result.endswith ("y") :
        result = result [:-1] + "ies"
    else :
        result += "s"
    return result