This may look OK, but it’s incorrect. As written, it means that all birds currently alive, as well as all birds that have ever lived, are very good at building the one nest they’ve all shared. That’s a big nest!

Nouns have to agree in number—start with plural, end with plural; start with singular, end with singular. This sentence should be:

Here’s another common mistake that the SAT will likely throw at you:

How can two people, Donna and Doug, become one beach bum? Well, they can’t:

Another commonly tested feature of nouns is countability. Look at the following sentences:

Both sentences are correct. Failings is something one could count; failings are discrete entities like pebbles or atoms or four-leaf clovers. Failure, however, cannot be counted; failure is an abstract state of being, like sorrow, liberty, and happiness. “I’ll take two happinesses please, just in case I break one”—if only! Concrete entities can be noncountable as well: air and water, to name two. (Putting on airs and parting the waters are figuratively countable uses of these noncountable nouns.)

Countability is most often tested via the less/fewer and number/amount pairings. Here’s a handy chart: