Words similar to hard

Example sentences for: hard

How can you use “hard” in a sentence? Here are some example sentences to help you improve your vocabulary:

For another, it's hard to make any changes that don't create a huge drop in revenues and/or even worse inequities: for instance, eliminating the marriage penalty straight-out would simply lower the tax rates on most wealthier households.
Power/type 2 error appears to be a major factor—if the genetic effect is sufficiently large ( HLA in Type 1 diabetes mellitus or CFH in age-related macular degeneration)—or, if the sample size is large, then there appears to be a greater chance of “hard” replication.
In Chapter 7, the authors discuss five topics that have traditionally been hard to understand from an evolutionary point of view.
“We've got all these ideas, and they turn out to be quite hard to test—there's no simple thing one can do on a single species.”
It is not really all that hard, I would explain to them.