1.across用作副词时基本意思是“在〔到〕对面”。与静态动词连用多表示位置“在对面”,与动态动词连用多表示位置“向对面”“从这一边到另一边”。
2.across与数量短语连用,置于单位名词之后,意为“…宽”,表示跨度。
3.across还可表示状态,意为“成十字形交叉状”。
4.across在句中主要用作状语,也可用作表语或宾语补足语。
5.across不用于比较等级。

across from
〈美〉在…的对面；在…另一边opposite
The statue is just across from the school.那个塑像就在学校对面。
They live just across from us.他们就住在我们对面。
Their house is just across from ours.他们的房子就在我们家的对面。
Our classroom is just across from yours.我们的教室就在你们的对面。

Can you swim across?你能游到对岸吗?
He turned his head and looked across at me.他转过头,打量着我。
The river is half a mile across.江面宽半英里。
He sat there quietly, with his arms across.他双臂交叉,静静地坐在那儿。
He began to talk, slipping the words across.他开始讲话,轻声把字吐出来。

across, cross
across与cross形近义同,但词性不同,前者用作介词或副词,表示一个穿越动作时要与一个实义动词连用; 后者用作动词,可单独表示穿越动作。

get across to,get through to
这两个短语都有“使…理解”之意，其区别在于get across to的宾语为一群人，而get through to的宾语为某个人。

［词源］＜中古英语acros(横过,交叉)

across the board
包括一切的，全体成员involving all members,groups or classes (of a company,an industry,a society,etc.)
This firm needs radical changes across the board.这家公司需要全面彻底大改组。
There will be a wage increase of 20 dollars a week across the board.全体员工每周工资将增加20美元。

She stared thoughtfully at the Englishman across the table.她若有所思地盯着桌子对面的那个英国人。
There's a hotel across the road.路的另一边有一家旅馆。
You can find deep knife scar across his face.你能发现横过他脸部的深深的刀疤。
She was wearing a silver fox fur across her shoulders.她肩上披了一张银狐皮。
A smile of pleasure passed across his face.他脸上掠过一丝快乐的微笑。
The ship sailed across the at lantic.这艘船横渡大西洋。
He swam across the river.他游过了河。
A straight line was ruled across the map.一条直线横划在地图上。
The two lines pass across each other atright angles.这两条线成直角相交。
His top teeth worked across the lower lip.他的上齿使劲咬着下唇。
This policy stretches across several different departments.这项政策影响着几个不同的部门。

across, along
参见along条。

across, beyond
参见beyond条。

across, over
这两个介词都可表示“在…另一侧”,有时可以互换。across表示从某一平面的一边至另一边; over表示从某障碍物的上面跨越过至另一侧。例如:
When I saw him, he was climbing over the fence.我看到他时,他正在爬越栅栏。
I helped the old lady across the road.我扶着老太太过了马路。

across, through
这两个介词均可用于“从一边到另一边的动作”。其区别是:across表示动作是在某一物体的表面进行的; through表示动作是在三维空间进行的,四面八方都有东西。
下面两个句子的意思不同:
河上有座桥。
There is a bridge across the river.
(桥横跨河上)
There is a bridge over the river.
(桥高出水面)

come across, drop across, fall across, run across
这四个短语的共同意思是“偶然遇到,碰到”。其区别是:
1.fall across的对象只能是人,不能是事物; 而come across, drop across和run across的对象可以是人,也可以是事物; run across的对象是事物时,只指令人不快的事物。
2.fall across不可用于被动结构。

cut across, cut through
这两个短语都指“抄近路走过”，cut across指从表面通过，其宾语一般比较宽广；而cut through则表示从物体内部穿过，具有快速穿越的意思。

在美国口语中, across还可表示“由…负责”。例如:
It is across you.这事由你负责。