For example, under the simple model p(w f |w e ), the English word "free" may be translated into the Japanese word 自 由 (as in free speech) or 無 料 (as in free beer) with equal 0.5 probability; this low probability may cause both translation pairs to be rejected by the dictionary extraction algorithm.
given p(w f |w e , t), where t is "politics" or "shopping", we can allow high probabilities for both words depending on context.