across       
 adverb, preposition uk/əˈkrɒs/ us/əˈkrɑːs/
A2 从一边到另一边;穿过;横过
from one side to the other of something with clear limits, such as an area of land, a road, or a river
  She walked across the field/road. 她穿过田野/横过马路。 
 They're building a new bridge across the river. 他们正在河上修建新桥。 
 When I reached the river, I simply swam across. 到河边后,我直接游了过去。 
 - More examples
 - He folded his arms across his chest.
 - Her books and clothes were packed into chests and shipped across to Canada.
 - Their hoofs threw up clods of earth as they galloped across the field.
 - On the eastern horizon, a huge cloud of smoke from burning oil tanks stretched across the sky.
 - Quigley clouted me smartly across the side of the head.
 
across          
preposition uk/əˈkrɒs/ us/əˈkrɑːs/
A2 在…的另一边;在…的对面
on the opposite side of
  The library is just across the road. 图书馆就在马路对面。 
  在…各处;在整个…;遍及
in every part of a particular place or country
  Voting took place peacefully across most of the country. 在这个国家大部分地区,选举进行得井然有序。 
 - More examples
 - There is a small wood just across the river.
 - Across the valley, troops were gathering.
 - Across the world, people are praying for peace.
 - My school is just across the road from where I live.
 - His workshop is just across the courtyard.