Knowledge bases may be used in the search engine to equate single terms. You should never use a predefined knowledge base (for example english) here as the clustering knowledge bases are not appropriate for search. Also you should never rephrase to or from more than a single term: doing so will lead to undefined behavior.
Every term of the text that is indexed and every term of that the user uses in a search will have the KBs (specified in the indexing configuration) applied. For example, you can rephrase honour to honor in the KB and then every time that honour appears in the text it will actually be indexed as honor and the search results will be identical if the user types either term (because it will always search for honor).
Great care must be exercised when you wish to change the KB. Because it is used at indexing time to permanently change the indexing, any change can lead to a mismatch between the terms that the user is searching and the terms that were indexed. To modify the KB you should follow this procedure: