The head-modifier cohesion term ℎ is used to penalize the distortion probability according to relationships between the head node and its children (modifiers).
we define ℎ as the product of probabilities for all head-modifier pairs taking as head node: , ∈ where } is the headmodifier cohesion relationship between and one of its child , ℎ is the corresponding probability, and are the aligned words for and .