A method and system are provided for query expansion. The method may include: providing a graph of question and answer word nodes generated from a set of training data for a given domain in the form of training question and answer texts, wherein the answer word nodes are disjoint words that do not occur in both a training question and an associated training answer and wherein edges are provided between a disjoint pair of a training question word and an associated training disjoint answer word, including providing weightings for the nodes and edges based on frequency data; and receiving a user query input, activating input nodes in the graph for words in the user query input, and applying spreading activation through the graph using the weightings to result in a top n most highly activated nodes that are used as candidate words for expansion of the user query input.