1. A method comprising: receiving a text item, the text item including one or more terms; determining a plurality of text strings, each text string including a matching portion and one or more suffixes, wherein the matching portion matches the text item, and the one or more suffixes are located after the matching portion; ranking the one or more suffixes based on a credibility score of each suffix and a frequency score of each suffix, the credibility score of a suffix indicating an estimated credibility of a source of the text string including the suffix, the frequency score of a suffix indicating an estimated frequency of appearance of the suffix, wherein the frequency score of the suffix is calculated based at least in part on a function measuring partial overlaps between at least a portion of the suffix and one or more other suffixes; and providing a group of the one or more suffixes that includes a highest ranking suffix for display as a suggestion for completing a sentence starting from the text item.