流行 (liú xíng) means “(of a contagious disease etc) to spread; to propagate; (of a style of clothing, song etc) popular; fashionable”. It is an HSK 4 Chinese word in the HSK 3.0 vocabulary.
这首歌现在很流行。
Zhè shǒu gē xiànzài hěn liúxíng.
This song is very popular now.
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