def _words_rhyme(word1, word2, letters):
    """
	Checks if two words rhyme when characters in letters variable are omitted
	:param word1: a word "kissa"
	:param word2: another word "kassi"
	:param letters: use consonants for assonance and vowels for consonance e.g ["a","e","i","o","u","y","ä","ö","å"]
	:return: True or False
	"""
    try:
        word1 = word1.lower()
        word2 = word2.lower()
        if word1 == word2:
            return False
        for letter in letters:
            word1 = word1.replace(letter, 'C')
            word2 = word2.replace(letter, 'C')
        word1 = word1.lstrip('C')
        word2 = word2.lstrip('C')
        if len(word1) < len(word2):
            temp = word1
            word1 = word2
            word2 = temp
        if len(word1) > len(word2):
            difference = len(word1) - len(word2)
            if word1[difference] != 'C' and word1[difference - 1] != 'C':
                difference = difference - 1
            word1 = word1[difference:]
        if word1 == word2:
            return True
        else:
            return False
    except:
        return False
