Across

Across is used as a preposition and as an adverb:
 It’s just not enough time to get across London.
(preposition)
[giving directions]
 A:  You keep going down until you get to the massive traffic-light complex. You know you’re at it. It’s sort of bright and there’s a big main road running across.
B:   Right.
(adverb)

  Across is not a verb. The verb form is cross:
 Every time you cross the road, you’re worried you’re going to get knocked over.
(Every time you across the road, you’re worried you’re going to get knocked over.)

Across can be used to indicate movement or position relative to two sides or extremes of something:
[referring to a newspaper article]
 In the paper there’s somebody who’s going to swim across the Atlantic four thousand miles.
 She sat facing me across the table.

When indicating position relative to another person or thing, with the meaning of ‘opposite’, ‘on the other side of the road to’, across is used with from:
 The Town Hall is across from the cathedral.

Across is often used in contexts of comparisons to indicate a range of something:
 The researchers carried out a study across 20 countries.

Across is also used to refer to the width or diagonal measurement of something. It follows the unit of measurement:
 First, a copy; he slipped a minidisk into the port, formatted and labelled it. Barely two centimetres across – easy to lose, but easy to hide.

Across is also used to refer to an area in which things are distributed:
 There are other smaller sites, scattered across the Caribbean and even in the Mediterranean.