The phrase "a serious difficulty" is correct and usable in written English.
You can use it when describing a significant problem or challenge that someone is facing.
Example: "The team encountered a serious difficulty in meeting the project deadline due to unforeseen circumstances."
Alternatives: "a major challenge" or "a significant problem."
And the fact that we don't behave anything close to perfectly is a serious difficulty".
From our perspective it would be a serious difficulty for Northern Ireland.
A serious difficulty is encountered in the above represented interpretation of geometry in that the rigid body of experience does not correspond exactly with the geometrical body.
Northern Ireland would face a "serious difficulty" if the United Kingdom votes to leaves the European Union, the Irish prime minister, Enda Kenny, has said.
But with the United States we had a serious difficulty with regard to night raids and civilian casualties, which has now improved after much work.
This year Enda Kenny, Ireland's outgoing taoiseach, said Northern Ireland would face a "serious difficulty" if the UK voted to leave the EU.
A more serious difficulty is that by organizing the book around various Journal scoops, Smith and Emshwiller give an unbalanced view of the underlying activity at Enron that was being exposed.
Then he raised a more serious difficulty: how to present the story's famous last line, when Gabriel imagines the snow falling on the graveyard where Michael Furey lies, and falling all across Ireland, "falling through the universe and falling, like the descent of their end, upon all the living and the dead".
A second serious difficulty is the problem of bias: we cannot justify the assumption that the sample of known features is random.
The No. 2 U.S. automaker faces a more serious difficulty stemming from the fallout over the recall of 6.5 million Firestone tires on its trucks and sports utility vehicles, most of which were installed on Ford Explorers.
There is also a less serious difficulty of explaining why the resulting function is one-to-one and onto intuitively this is just a matter of winding numbers if one can approximate U from inside by domains with smooth or piecewise-smooth closed curve boundaries.
