Storms sweep across the ocean and pile up great waves.

Storms sweep across the ocean and pile up great waves.
across是介词还是副词?

介词：介词的基本用法 介词的基本用法 介词 (preposition) 又称前置词,是英语中最活跃的词类之一,它表示的是它后面的名词或代词(或相当于名词的其他词类、短语或从句)与其他句子成分的关系.介词可分为下列三类：1.简单介词,如：about,above,across,after,against,among,at,before,behind,below,beneath,beside,besides,beyond,but,by,down,during,except,for,from,in,like,near,of,off,on,over,past,round,since,through,to towards,under,until,till,up,with 2.合成介词,如：inside,into,onto,outside,throughout,upon,within,without 3.短语介词,如：according to,along with,apart from,as for,as to,because of,by means of,in front of,in spite of,instead,in accordance with,on account of,on behalf of ,owing to,due to,together with,up to,with regard to,next to,prior to 介词不能单独充当句子成分,它必须与名词或相当于名词作用的成分构成介词短语才能充当 句子的成分.定语:在句中修饰名词或代词的成分叫定语.用作定语的主要是形容词,代词,数词,名词,副词,动词不定式,介词短语等.形容词,代词,数词,名词等作定语时,通常放在被修饰的词前面.Heisanewstu'dent.他是个新生.但副词,动词不定式,介词短语等作定语时,则放在被修饰的词之后.Thebikeintheroomismine.房间里的自行车是我的.副词:副词是一种用来修饰动词,形容词,副词或全句的词,说明时间,地点,程度,方式等概念.分 类:1) 时间和频度副词:now,then,often,always,usually,early,today,lately,next,last,already,generally,frequently,seldom,ever,never,yet,soon,too,immediately,hardly,finally,shortly,before,ago,sometimes,yesterday.2) 地点副词:here,there,everywhere,anywhere,in,out,inside,outside,above,below,down,back,forward,home,upstairs,downstairs,across,along,round ,around,near,off,past,up,away,on.3) 方式副词:carefully,properly,anxiously,suddenly,normally,fast,well,calmly,politely,proudly,softly,warmly 4) 程度副词:much,little,very,rather,so,too,still,quite,perfectly,enough,extremely,entirely,almost,slightly.5) 疑问副词:how,when,where,why.6) 关系副词:when,where,why.7) 连接副词:how,when,where,why,whethe