  Vector space methods that measure semantic similarity and relatedness often
rely on distributional information such as co--occurrence frequencies or
statistical measures of association to weight the importance of particular
co--occurrences. In this paper, we extend these methods by incorporating a
measure of semantic similarity based on a human curated taxonomy into a
second--order vector representation. This results in a measure of semantic
relatedness that combines both the contextual information available in a
corpus--based vector space representation with the semantic knowledge found in
a biomedical ontology. Our results show that incorporating semantic similarity
into a second order co--occurrence matrices improves correlation with human
judgments for both similarity and relatedness, and that our method compares
favorably to various different word embedding methods that have recently been
evaluated on the same reference standards we have used.
