Removing bias from features containing overlapping embedded grammars in a natural language understanding system

A method of removing bias from an action classifier within a natural language understanding system can include identifying a sentence having a target embedded grammar that overlaps with at least one other embedded grammar and selecting a group of overlapping embedded grammars including the target embedded grammar and at least one additional embedded grammar. A sentence expansion can be created that includes the sentence including the target embedded grammar and a copy of the sentence for each additional embedded grammar of the group. Each copy of the sentence can include a different additional embedded grammar from the group in place of the target embedded grammar. The sentence expansion can be included within action classifier training data.