1、fast的比较级是：faster。fast，adj. 快的；迅速的；紧的；牢固的；放荡的。adv. 快速地；紧紧地；放荡地；深深地。n. 斋戒；禁食；系泊用具。

2、He ran fast enough to catch the thief.他跑得飞快，足以抓住那小偷。

3、The priest had only water and bread during his three week fast.牧师在三个星期的斋戒期间只进食水和面包。