A question answering system includes a similar-question generation unit, a
first search unit, a second search unit, and an answer selection unit.
The similar-question generation unit selects a feature word from an input
question to generate a transformational question in which the feature
word is replaced with another word. The first search unit executes a
first search process based on the transformational question. The second
search unit selects a word included in a first search result acquired as
an extension word and executes a second search process with using the
selected extension word. The answer selection unit analyzes a
correspondence relation among extension words included in a second search
result, determines the feature word and a constructive part of an answer
equivalent word in the second search result based on an analysis result,
and selects a word determined to be an answer.