cross与across都作“穿过”解，但是用法上有差异。
1. cross是个及物动词，可以作谓语。
cross (over) (from…) (to/into…) | ~ (over) (sth)
穿越；越过；横过；渡过
He crossed the road.他穿过了马路。
Look left and right before you cross the road.
左右看一看，然后再过马路。
Look both ways before crossing the road.
横过马路前要朝左右两边看一看。
Be careful not to cross the line.
小心别越过道路的中界线。
Be careful crossing the main road.
过大马路时小心点儿。
Give me your hand while we cross the road.
过马路时拉着我的手。
She was partly to blame for failing to look as she crossed the road.
她过马路时没注意看，负有部分责任。
I crossed the river by the wooden bridge.
我走这座小木桥过了河。
They crossed the finishing line together.
他们同时越过终点线。
The two horses crossed the finishing line together.
两匹马同时越过终点线。
We crossed from Dover to Calais.
我们从多佛尔横渡到加来。
He crossed over the road and joined me.
他穿过马路和我走到了一块儿。
The bridge crosses the River Dee.
这座桥横跨迪河。
We crossed the bridge over the river Windrush.
我们穿过了温德拉什河上的桥。
A look of annoyance crossed her face .
恼怒的神色从她脸上掠过。
Berg tilts his head and a mischievous look crosses his face.
伯格侧着头，脸上掠过一丝调皮的神情。
2.across是介词，不可作谓语。
I walked across the Park.我走过了公园。
He took her across the road.
他扛着她穿过了马路。
She took her arm and guided her across the busy road.
她挽着她的手臂领她横穿过繁忙的公路。
You can fly across the U.S.in about five hours.
你可以在5 个小时左右飞越美国,
He walked across the field.
他走过田地。
She walked across the floor and lay down on the bed.
她走过地板躺在了床上。
He offered to ferry us across the river in his boat.
他提出坐他的船把我们渡过河。
We left the road and struck off across the fields.
我们下了公路，穿过旷野往前走。
The lights changed to red before I could get across.
我还没来得及通过，红灯又亮了。
The bridge was destroyed so we couldn't get across the river.
大桥已经毁坏，我们无法过河了。
The general had to get his troops across the river.
将军必须让部队过河。
When my name was called, he looked across at me.
当叫到我名字的时候，他从那边朝我看过来。
They went on a long train journey across India.
他们乘火车作了一次横跨印度的长途旅行。
I could hear his pen scraping across the paper.
我听得见他的钢笔在纸上沙沙地响。
We want to cut across lines of race, sex and religion.
我们要超越种族、性别和宗教的界限。