because/as/for/since.导航词义：因为，由于

1. because:conj. 因为.语气最强，表示因果关系，通常用来回答由 why 引导的疑问句。由 because 引导的分句置于句首时，须用逗号与主句隔开，置于句末时则不用隔开。

because the traffic is so busy, she failed to arrive at the station on time.

因为路上交通太拥挤，她没能准时赶到车站。

He came back late because there was something wrong with his car.

他回来晚了，因为汽车出了故障。

2. as:conj. 因为，由于.如果所述理由是明显的或者已知的，则用 as 较 because 更为合适。

As it's raining, you'd better stay at home.

既然在下雨，你最好呆在家里。

He puts the ice cream into the fridge immediately, as it melts easily.

他马上把冰激凌放进冰箱，因为它很容易化掉。

3. for:conj. 因为.for 属于并列连词，由它引导的分句表示补充说明性的理由，通常只能置于句末，且必须用逗号与前面的分句隔开。

He must have passed this way, for here are his footprints.

他肯定是从这条路走过去的，这里有他的脚印。

He has to work hard, for he wants to support his family.

因为要养家糊口，他必须努力工作。

4. since:conj. 因为，既然.当所述原因是已知的客观事实或被当作推断的理由时用 since，语气略强于 as。

Since he is absent, let's begin.

既然他不在，我们就开始吧。

Susan must have come back home, since her coat is not in the wardrobe.

苏珊肯定回过家，因为她挂在衣橱里的外套不见了。

全部

1·They are here because of us.

他们是因为我们来这里的。《牛津词典》

2·She resigned because of ill health.

她因健康状况不佳而辞职。《牛津词典》

3·I was angry because I played so badly.

我生气因为我弹得这么糟。《柯林斯英汉双解大词典》

4·The road is closed because of the snow.

这条路因下雪而封闭。《牛津词典》

5·Many diets fail because they are boring.

许多规定饮食因单调乏味都不奏效。《牛津词典》

6·He walked slowly because of his bad leg.

他因为腿不方便而行走缓慢。《牛津词典》

7·She's been off work because of sickness.

她因病没有上班。《牛津词典》

8·They abandoned the match because of rain.

因为下雨，他们中止了比赛。《牛津词典》

9·Feed the dogs because they haven't eaten.

喂喂这几条狗，因为它们还没吃呢。《柯林斯英汉双解大词典》

10·She had left him because of his drinking.

她离开了他，因为他酗酒。《柯林斯英汉双解大词典》

因为

1·I was angry because I played so badly.

我生气因为我弹得这么糟。《柯林斯英汉双解大词典》

2·He walked slowly because of his bad leg.

他因为腿不方便而行走缓慢。《牛津词典》

3·They abandoned the match because of rain.

因为下雨，他们中止了比赛。《牛津词典》

4·I didn't get it because it cost too much.

因为那东西太昂贵我没买。《牛津词典》

5·She had left him because of his drinking.

她离开了他，因为他酗酒。《柯林斯英汉双解大词典》

由于

1·Filming was delayed because of bad weather.

由于天气恶劣拍摄受阻了。《牛津词典》

2·Our plans fell through because of lack of money.

我们的计划由于缺钱而落空了。《牛津词典》

3·Their pay was late because of a computer bungle.

由于计算机出错，他们的工资晚发了。《牛津词典》

4·They got off scot-free because of lack of evidence.

由于证据不足，他们得以逍遥法外。《牛津词典》

5·This show will run and run because it's a class act.

由于盛誉绵绵，这台演出将继续爆满。《柯林斯英汉双解大词典》

因

1·She resigned because of ill health.

她因健康状况不佳而辞职。《牛津词典》

2·Many diets fail because they are boring.

许多规定饮食因单调乏味都不奏效。《牛津词典》

3·She had scratched because of a knee injury.

她因膝伤退出了比赛。《牛津词典》

4·She was marked down because of poor grammar.

她因语法不好被扣了分。《牛津词典》

5·Many families break up because of a lack of money.

许多家庭因缺钱而破裂。《柯林斯英汉双解大词典》

(1)because ofadv. 因为；由于