This type of format definition is an error-tolerant algorithm where expressions are separated into three character groups called trigrams.

For example, a search for brain creates these trigrams: bra, rai, and ain. Consequently, the search finds matches of brain, rain, train, and again. Of these matches, only one has all three trigrams, so brain is returned as the result with the highest confidence.

Use this format definition to account for OCR errors in a document, for short phrases, or a phonetic search.