A Translation Memory is a collection of perfectly aligned source and target segments of sentences from previously translated documents, which help the translator maintain coherence and speed up the translation process. CAT tools use Translation Memories to assist translators during the translation process. They can either help pretranslate automatically segments of sentences of the new documents to be translated if such segments are 100% similar to the previously translated source segments or they can provide useful suggestions to the translator if the correspondence is usually between 70/75% and 99% (these are called fuzzy matches).