To help address the issue of OOV words and lexical variations, we perform clustering to group together words which are distributionally similar (Brown et al., 1992;Turian et al., 2010).
we perform hierarchical clustering using Jcluster (Goodman, 2001) on 52 million tweets; each word is uniquely represented by a bit string based on the path from the root of the resulting hierarchy to the word's leaf.