Sometimes things are not what they seem to be. This is the case with un par. The exact translation is “a pair”, and in Spanish a pair it’s actually two, but the use that we give to the expression un par it’s a little bit different.
Un par is closer to “a couple”, rather than “a pair”. When an Argentinean says something like “Me voy de viaje por un par de días” (I’m going for a trip for a pair of days), he or she are trying to say that is going away for a few days, for a couple of days, not exactly 2.
So if you want to ask for something in a store, don’t say un par, unless you’re willing to take 3, 4 maybe 5. If you want to take only 2, just say 2!
– ¿Me pasas un par de clavos? (can you hand a couple of nails?). This person is actually asking for a small handful of nails, not just 2.
Un par is actually a pair when it comes to shoes. When someone says “Me compré un par de zapatos” (I bought a new pair of shoes) it actually means a pair.