句子成分，顾名思义，就是句子的组成部分。考生在备考ACT英语考试的时候，如果能对句子成分有比较周全的了解，那么对考生的备考而言还是很有帮助的，留学360提醒考生：总体来说，英语中的句子成分共有六种，分别如下：
1、主语(Subject)是一个句子中的主体，常由名词、代词或者起同等作用的词语充当，一般置于句首。如：
The sun rises in the east.I love English very much.
Seeing is believing. 眼见为实。
2、谓语(Predicate)用来说明主语的动作或者状态，常由动词充当，位于主语之后。如：
It was raining when she arrived at the airport.
She accepts his proposal at last.
3、宾语(Object)指承担谓语动作的对象，常由名词、代词或者同等作用的词语担任，置于及物动词或者介词之后。如：
She only eats an apple every morning to lose weight.
Our parents love us heart and soul.
He is extremely fond of swimming.
4、补语(Complement)和表语(Predicative)，补语用来对主语和宾语进行补充，以使其意思更加完整，一般主要说明主语或宾语的特征，常由名词或形容词担任。表语即是连系动词(be动词、become等词)后面的主语补语。如：
Jane was declared the champion of the match.(主语Jane的补语)
People consider the plan feasible.(宾语plan的补语)
The young lady is elegant.(表语，表明主语The young lady的特征)
Lucy was a teacher before she came to China.(表语，指出主语Lucy的身份)
5、定语(Attribute)用于限定或者修饰名词或者其他相当于名词作用的词语，常由形容词、相当于形容词的短语或者从句充当。形容词常置于名词之前，其他两种定语则位于名词之后。如：
The young lady picked him up every afternoon.
She has a great desire to travel around the world.
The boy who wears a pair of glasses is Harry Porter.
6、状语(Adverbial)用于修饰动词、形容词、副词乃至整个句子，常由副词或者具有同等作用的短语或从句充当。如：
Lily performed well in the contest.
Honestly, I do not know how to solve this problem.
As time goes by, we have a much better understanding of each other.
有时候，形容词或者过去分词也可以充当状语，如：
Cold and hungry, the little girl died in the night.
Preoccupied with his work, he has no time to care for his family.
以上六种句子成分就是ACT English必备的，希望考生在备考ACT英语考试的时候能重点掌握，ACT英语成绩高分的取得需要考生做好充分的备考工作，希望考生可以重视。