Chinese · Pronunciation Guide
tsao with a strong puff of air, low and sagging. The c is an aspirated "ts", not an English c.
cǎo
The next syllable decides. Its close neighbour is 早 zǎo, which shares the vowel and the tone and differs only in aspiration — one has a puff of air and the other does not. Grass and early are otherwise identical, which makes the breath genuinely load-bearing.
Listen: 草
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孩子们在草地上玩。
Háizimen zài cǎodì shàng wán.
The children play on the grass.
Listen: 孩子们在草地上玩。
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孩子们在草地上玩。 keeps cǎo at a full dip because dì falls. Before it, hái climbs and zi and men both fade; after it, dì and shàng both plunge and wán climbs. So the sentence has one dipping tone and it does not convert, since neither neighbour dips.
Treating the letter c as English "k" or "s" gives kǎo or sǎo, both real words. Start with an audible "ts". Under-aspirating gives zǎo, which as noted is the word for early. And the long glide gets shortened, which robs the dipping tone of the space it needs to descend and lift.