in short supply

not easily obtainable; scarce

供應不足，短缺

he meant to go, but time and petrol were in short supply.

他想要走，但時間和汽油都不夠了。

on supply

(of a schoolteacher) acting as a temporary substitute for another

（學校教師）代課

supply and demand

the amount of a good or service available and the desire of buyers for it, considered as factors regulating its price

（商品，服務的）供應與需求，供求

by the law of supply and demand the cost of health care will plummet.

根據供求關系定律，保健費用將會驟降。