1 (wiktionary) 2 (zh.wikipedia) 3 (en.wikipedia) 4 (glosbe)

Compounds Expand your vocabulary by studying more complex words built by the 'core words'.

HSK 3.0 (2022)	Big5	Gb	Pin	Eng
1	有時候	有时候	yǒushíhou	from time to time, on_occasion, occasionally, somewhile, otherwhile, now and again, sometimes, now and then, at times, on occasion, whiles, once in a while
5	偶爾	偶尔	ǒuěr	once in a blue moon, from time to time, hardly ever, every so often, now and again, seldom, infrequently, on occasion, rarely, betweenwhiles, scarcely, unusually, occasionally, sporadically, every now and then, at times, now and then, once in a while