"The" ends with a vowel and that vowel's sound changes. "the book" When it is before a consonant, it is pronounced like "a" in "above", "a" in "ago", the first "o" in "composer". Also, make sure that you finish pronouncing "the" before starting to pronounce the following word. "the astronaut" When it is before a vowel, it is pronounced like "y" in "city", "ee" in "feet". Also, keep pronouncing the end of "the" as you start the pronunciation of the following word, almost like the two words are one word. It would be better if we used symbols from the International Phonetic Alphabet.