HSK 1.0 (1992)	Big5	Gb	Pin	Eng
A	經常	经常	jing1chang2	often/ frequently/ constantly/ usually
C	不停	不停	bu4ting2	ceaselessly/ constantly/ on and on
C	時時	时时	shi2shi2	time and time again/ constantly/ very often
D	不定	不定	bu4ding4	inconstantly

HSK 2.0 (2010)	Big5	Gb	Pin	Eng
2		长	chang2	length/ long/ forever/ always/ constantly
3		经常	jing1 chang2	day to day/ everyday/ daily/ frequently/ constantly/ regularly/ often
5		不断	bu4 duan4	unceasing/ uninterrupted/ continuous/ constant
5		时刻	shi2 ke4	moment/ CL:個|个[ge4]/ constantly/ always
6		一贯	yi1 guan4	consistent/ constant/ from start to finish/ all along/ persistent
6		一向	yi1 xiang4	all along/ the whole time/ constantly/ earlier/ lately
6		精益求精	jing1 yi4 qiu2 jing1	to perfect sth that is already outstanding (idiom)/ constantly improving

HSK 3.0 (2022)	Big5	Gb	Pin	Eng
2	經常	经常	jīngcháng	everyday, daily, alway, often, a great deal, frequently, sempre, much, regularly, constantly, evermore, day-to-day
6	時時	时时	shíshí	always, constantly, often
7	精益求精	精益求精	jīngyìqiújīng	to perfect sth that is already outstanding (idiom), constantly improving
7	念念不忘	念念不忘	niànniàn-bùwàng	to keep in mind constantly (idiom)
7	千變萬化	千变万化	qiānbiàn-wànhuà	countless changes, constant permutation

地球在不断地演变。 The earth is constantly evolving . 地球 在 不断 地 演变 。 (ENG ) (ZH ) (0880)

水汽不停地在蒸发。 The steam is constantly evaporating . 水汽 不停 地 在 蒸发 。 (ENG ) (ZH ) (2761)

She is constantly writing letters .

她不断地写信。

她不断地写信。