def decrypt(word):
    """
    Enter your function docstring here
    parameters: word (string)
    """
    # decrypt a single word from the secret language
    if word[0] in ('a', 'e', 'i', 'o', 'u') and word[-3:] == 'tan':
        word_sans_tan = word[:-3]
        return word_sans_tan
    elif word[0] not in ('a', 'e', 'i', 'o', 'u') and word[-3] == 'est':
        word_sans_est = word[-4] + word + word[-4:]
        return word_sans_est
    else:
        # If the word is not a valid word in the secret language, return None
        print('None, invalid message')