The constituency parse tree serves as an input to the syntactic encoder (Section 3.3). The first step is to remove the leaf nodes which contain meaning representative tokens (Here: What is the best language …). H denotes the height to which the tree can be pruned and is an input to the model. Figure 2(a) shows the full constituency parse tree annotated with vector a for different heights. Figure 2(b) shows the same tree pruned at height H = 3 with its corresponding a vector. The vector a serves as an signalling vector (Section 3.4.2) which helps in deciding the syntactic signal to be passed on to the decoder. Please refer Section 3 for details.