Dire straits are tricky for ships to navigate, and have come to more broadly mean a bad situation. 'Dire straights' is a spelling error, and means bad form on the part of the writer.
Photo: Victor Schiferli
We recently examined the case of whether 'straitjacket' or 'straightjacket' was the correct spelling (short answer: use either but be consistent).
While the same issue exists here -- people choose 'straight' because it's a more common word than 'strait' -- the get-out-of-linguistic-jail clause does not apply this time around. 'Dire straits' is the only correct spelling. 'Dire straights' is a mistake. Yes, that represents a level of inconsistency. English spelling is rarely straightforward. Get used to it.
This is not a mistake anyone of my age is particularly likely to make, if only because the band Dire Straits was so omnipresent in Australia in the mid-1980s. Younger folk don't have that advantage; like Mark Knopfler, you'll simply have to practise until you get it right. Thanks KM for the topic suggestion.
Lifehacker's Mind Your Language column offers bossy advice on improving your writing.