The following video demonstrates each syllable of the pinyin structure
and the exercise of pinyin/zhuyin with basic Chinese 4-tune pronunciation

Mandarin pinyin tunes
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rūn, rún, rǔn, rùn

fourth tune

rùn

intercalary 閏 rùn

leap year; bissextile 閏年 rùn nián
intercalary 閏 rùn	year 年 nián

glossy; sleek; smooth lubricate; moisten; embellish 潤 rùn

lubricate; lubrication 潤滑 rùn huá
lubricate 潤 rùn	smooth 滑 huá