to forget; to cease to think about (sb or sth) anymore

unforgettable

forgetful

to keep in mind constantly (idiom)

to gradually forget as time passes; to have (sth) fade from one's memory

to be forgetful; to have a short memory

Don't forget! (literary)

never to be forgotten

see 沒齒難忘|没齿难忘[mo4 chi3 nan2 wang4]

hard to forget even after one's teeth fall out (idiom); to remember a benefactor as long as one lives; undying gratitude

an eminent person has short memory (idiom)

to have a highly retentive memory; to have sth imprinted in one's memory

don't forget your friends when you become rich