1. Across indicates the direction of movement from one side of an area to the other.
Pattern: motion verb + across + noun
The girl ran across the yard.
Verbs often used before across:
crawl, drive, go, limp, move, ride, run, swim, walk
2. Across can mean on the other side of a place.
Pattern: verb + across + noun
My friend lives across the street.
3. Across from means opposite or facing.
Pattern 1: verb + across from + noun
My assistant's office is across from mine.
My secretary sits across from me.
Pattern 2: verb + across + noun + from + noun
My assistant's office is across the hall from mine.
4. Across and all across mean in every area of.
People across the world are using the Internet.
There is a heat wave all across the country.
across the board—including everyone or everything
Everyone got a raise in salary: there was a wage increase of three percent across the board.
5. Phrasal verbs
come across (nonseparable)—find something unexpectedly
I came across this old picture of you when I was looking for some documents.
come across (intransitive)—be received by an audience
The banquet speaker was not sure how well he came across.
run across (nonseparable)—to find something unexpectedly
I ran across a letter you wrote to me when we were children.
get (something) across to (separable)—make something understood
The young girl tried to get it across to her boyfriend that she was not ready to get married.