Although the International Baccalaureate thinks 0 to be a natural number. Oxford Dictionary says "a positive whole number such as 1, 2, or 3, and sometimes also zero".
ɔ l ð oʊ WORD_BOUNDARY ð ɪ WORD_BOUNDARY ɪ n t ə ɹ n æ ʃ ə n ə l WORD_BOUNDARY b æ k ʌ l ɔ ɹ iː eɪ t WORD_BOUNDARY θ ɪ ŋ k s WORD_BOUNDARY z iə ɹ oʊ WORD_BOUNDARY t ə b i WORD_BOUNDARY ʌ WORD_BOUNDARY n æ t̠ʃ ə ɹ ɹ ə l WORD_BOUNDARY n ʌ m b ə ɹ ɹ WORD_BOUNDARY ɑ k s f ə ɹ d WORD_BOUNDARY d ɪ k ʃ ə n ɛ ɹ i WORD_BOUNDARY s ɛ z WORD_BOUNDARY ʌ WORD_BOUNDARY p ɑ z ɪ t ɪ v WORD_BOUNDARY h oʊ l WORD_BOUNDARY n ʌ m b ə ɹ WORD_BOUNDARY s ʌ t̠ʃ WORD_BOUNDARY ʌ z WORD_BOUNDARY w ʌ n WORD_BOUNDARY t uː WORD_BOUNDARY ɔ ɹ WORD_BOUNDARY θ ɹ iː WORD_BOUNDARY æ n d WORD_BOUNDARY s ʌ m t aɪ m z WORD_BOUNDARY ɔ l s oʊ WORD_BOUNDARY z iə ɹ oʊ WORD_BOUNDARY