the 什么时候读 /ðə/、什么时候读 /ði/

If it's not stressed, the pronunciation of the word 'the' will change depending on the word that follows. If the next word begins in a consonant sound, it's pronounced /ðə/. But if the next word begins in a vowel sound, it's pronounced /ði/.

看的是读音，不是字母：the one 里 one 拼写以 o 开头，可读音以 /w/ 开头，所以用 /ðə/；the hour 里 hour 以字母 h 开头，可 h 不发音，读音以元音开头，所以用 /ði/。这和 a / an 的规则一样。

/ði/ 后面接元音时，还会自然带出第 2 课讲过的轻 /j/：the orange 读成 thee-yorange。