This can be used to describe that some thing is supposed to be done. (should, ought to).
動詞の辞書形 + べき
例 －
１．ゴミはゴミ箱に捨てるべきです。
(gomi wa gomibako ni suteru beki desu)
(we should throw the garbage into the garbage can)
２．お金を拾ったら警察に持って行くべきです。
(okane wo hirottara keisatsu ni motte iku beki desu)
(if you pick up money, should take it to the police)
3．お年寄りが乗ってきたら、席を譲るべきだと思います。
(otoshiyori ga notte kitara, seki wo yuzuru beki da to omoimasu)
(I think, we should offer our seats when an elderly person is on board )
4．学生は勉強だけではなく運動もするべきです。
(gakusei wa benkyou dake dewanaku undou mo suru beki desu)
(not only studies, students should do sports too)
5．授業中は居眠りするべきではありません。
(jugyouchuu wa inemurisuru beki de wa arimasen)
(we should not doze in the class)
