1.warn
If you warn someone about something such as 【a possible danger or problem】,you tell them about it so that they 【are aware of】 it.警告; 提醒
如：When I had my first baby friends warned me that children were expensive.
當(dāng)我有了第一個(gè)孩子時(shí),朋友們提醒我說(shuō)養(yǎng)小孩是很花錢的.
2.alert If you alert someone to a situation,especially 【a dangerous or unpleasant situation】,you 【tell them about it】.向…發(fā)出警報(bào)
如：
He wanted to alert people to the activities of the group.
他想警告人們注意這個(gè)組織的行動(dòng).
注意1和2,warn只是警告可能會(huì)發(fā)生的情況,而alert是知道危險(xiǎn),發(fā)出的警報(bào)!
3.for the sake of 為了……起見(jiàn).為了…的利益 【表示的是目的】
如：for the sake of relaxation 為了達(dá)到放松的目的
4.because of 由于 【只是解釋原因】
如：He came back early because of the rain .
由于下雨,所以他回來(lái)得早.