For transliteration options that are TM-unknown, the p w (h, u) and p w (u) factors becomes zero and the translation model probability as given by equation (13) becomes: In such cases the λ factor cancels out and no weighting of word translation vs. transliteration  Table 6: Applying Heuristic 3 and its Combinations with other Heuristics to Model-2 occurs anymore.
of this, transliterations are sometimes incorrectly favored over their translation alternatives.