About Translation Memory Matches

When SDL Trados Studio performs a lookup, it compares the content of the current source document segment against segments of the same language in the translation memory. It looks for translation memory segments which have enough content in common with the document segment for the segment translation held in the translation memory to be of use when translating the document segment.

The degree of match between the source document segment and a translation memory segment is expressed as a percentage figure. For example, if the content of a translation memory segment matches the document segment exactly, that is a 100% match. To qualify as a 100% match, the entire content (all characters and character formatting) of both the source document segment and the translation memory segment must match exactly.

Where a document segment and a translation memory segment match exactly and also have the same document context, this is a context match.

A less than 100% match is a fuzzy match. In theory, a fuzzy match could be anything between 99% and 1%. However, there is a point below which there is insufficient usable content in the translation for it to be of use. This cut-off point is known as the 'fuzzy match threshold'.

Fuzzy Match Threshold

The default fuzzy match threshold for SDL Trados Studio is 70%. This means that when the degree of match between a source document segment and a translation memory segment is less than 70%, they are treated as having no match at all. The fuzzy match threshold is a setting that can be raised or lowered.

To set the fuzzy match threshold for your:

Context Matches

A context match is better than a 100% match. To be a context match, the translation memory segment must be a 100% match for the document segment and the two segments must have the same document context. For the document segment and the translation memory segment to have the same context, they must both have been preceded by the same segment.

Context matching is possible because context information is stored in the translation memory. When you add a new translation to a translation memory, three segments are added:

Context segments cannot be seen when you view the contents of the translation memory.


A PerfectMatch is a form of context match that compares updated source files to a corresponding set of old bilingual documents rather than to a translation memory. Segment matches, known as PerfectMatch units (XUs), are checked for context, that is, the surrounding entries are checked to ensure that they are the same. They are then extracted from the old bilingual documents and transferred to the updated source files. Because the PerfectMatch segment matching process includes a check for context, XUs typically need no further translation or editing during translation.



PerfectMatch cannot be performed in SDL Trados Studio, however if you include TradosTag (TTX) files in your SDL Trados Studio project that have been pre-translated in earlier versions of SDL Trados, PerfectMatch data pertaining to those files can be displayed.



Related Topics

How to Perform a Lookup and Apply Translations