刀不磨要生銹，人不學要落後

a blade will get rusty if it is not sharpened; a man will fall behind if he doesn't study (idiom)

knife / blade / single-edged sword / cutlass / CL:把[ba3] / (slang) dollar (loanword) / classifier for sets of one hundred sheets (of paper) / classifier for knife cuts or stabs

no; not so / (bound form) not; un-

to rub / to grind / to polish / to sharpen / to wear down / to die out / to waste time / to pester / to insist

grindstone / to grind / to turn round

to demand / to request / to coerce

important / vital / to want / to ask for / will / going to (as future auxiliary) / may / must / (used in a comparison) must be / probably / if

(bound form) to demand; to coerce

to want; to need; to ask for / will; shall; about to / need to; should / if (same as 要是[yao4 shi5]) / (bound form) important

to be born / to give birth / life / to grow / raw / uncooked / student

to rust / to grow rusty / to corrode / oxidization

to corrode / to rust

person; people / CL:個|个[ge4],位[wei4]

to learn / to study / to imitate / science / -ology

to leave out / to be missing / to leave behind or forget to bring / to lag or fall behind

colloquial reading for 落[luo4] in certain compounds

to fall or drop / (of the sun) to set / (of a tide) to go out / to lower / to decline or sink / to lag or fall behind / to fall onto / to rest with / to get or receive / to write down / whereabouts / settlement

to fall behind / to lag (in technology etc) / backward / to retrogress

back / behind / rear / afterwards / after / later / post-