In the following examples, a preposition has been added to the beginning of the original word, making it more specific.

  NOUNS                         

  by-line—a line at the beginning of an article with the author's name
His article was published, and he was pleased to see his name on the by-line.            

  bypass —a route that goes around a city, rather than through it
Taking the bypass saves a lot of time. 

  bypass —a surgical operation that avoids the main organ
Her father had a heart bypass last month.                                     

  back-up—someone who can substitute if necessary
I think I am well enough to do the job; if not, my colleague is here as a back-up.

  downgrade—a change to a lower quality
His new position is a downgrade in salary, but he is happier.          

  downpour—a heavy rain
The streets are flooded after that downpour yesterday.            

  downtown—the heart of a city
Let's go downtown tonight and have fun.           

  downswing—a reduction in business activity
There was a downswing in the first quarter of the year.           

  input—the contribution of ideas
We really need your input for this proposal.           

  off-chance—an unlikely possibility
He called me on the off-chance that I would be available.            

  off-shoot—a branch
That group is an off-shoot of a national organization.           

  outbreak—an eruption
There has been an outbreak of the flu in this city.          

  outlaw—a criminal
The cowboy films always have heroes and outlaws.          

  outpost—a place of business far away from city life
His store is a little outpost in the middle of nowhere.           

  outpouring—an abundance
There was an outpouring of sympathy for the widow.           

  output—production
Our output for the month was huge; we made a lot of money.           

  overkill—failure caused by too much effort
The salesman talked so much that the client lost interest; it was complete overkill.

  overpass—a bridge that extends over a road
An overpass is being built at that intersection; it will ease the traffic situation.

  throughway—highway
You should go on the throughway; it's much faster.       

  underdog—the team or person not expected to succeed
It's exciting when the underdog wins in a tournament.           

  underpass—a road built underneath another road
To get on the main highway, you need to get on the underpass first.           

  underpinnings—foundation
If the underpinnings are strong, the building will be safe.          

  update—the latest information
The television stations are giving us an update on the tragedy every five minutes.

  upheaval—a disruption
There is a big upheaval going on in our office; a lot of people are being transferred.

  upstart—ambitious newcomer
The new assistant tried to change our office procedures during her first week. What an upstart!                       

  upsurge—increase in activity
There was an upsurge during the second quarter, thank goodness!            

  upswing—increase in activity
There has been a steady upswing this year.                                                                                                 

 Certain expressions use prepositions in noun form.          

  the ins and outs—all of the details
After owning a restaurant for twenty years, he knows all the ins and outs of the business.

  the ups and downs—the good things and the bad things
We learn to cope with the ups and downs of life.                     

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