Word difficulty is usually measured by vocabulary lists or word length.
w ɜː d WORD_BOUNDARY d ɪ f ɪ k ʌ l t i WORD_BOUNDARY ɪ z WORD_BOUNDARY j uː ʒ uː ə l i WORD_BOUNDARY m ɛ ʒ ə ɹ d WORD_BOUNDARY b aɪ WORD_BOUNDARY v oʊ k æ b j ʊ l ɛ ɹ i WORD_BOUNDARY l ɪ s t s WORD_BOUNDARY ɔ ɹ WORD_BOUNDARY w ɜː d WORD_BOUNDARY l ɛ ŋ θ WORD_BOUNDARY