Given monolingual text in a new domain, OOVs are easy to identify, and their translations can be acquired using dictionary extraction techniques (Rapp, 1995;Fung and Yee, 1998;Schafer and Yarowsky, 2002;Schafer, 2006;Haghighi et al., 2008;Mausam et al., 2010;Daumé III and Jagarlamudi, 2011), or active learning (Bloodgood and Callison-Burch, 2010).
previously seen (even frequent) words which require new translations are harder to spot.