1. A method comprising: receiving, from a client computer, a first request comprising a partial search term for an item, wherein the partial search term comprises one or more characters; selecting a first plurality of predicted completions of the partial search term based, at least in part, on the partial search term, wherein each predicted completion in the first plurality of predicted completions is associated with a category of a set of categories; wherein the first plurality of predicted completions comprises: a first set of categorized completions associated with a first category among the set of categories, and a second set of categorized completions associated with a second category among the set of categories; determining a highest first selection ratio for the first set of categorized completions associated with the first category wherein the highest first selection ratio is greater than a first threshold value based, at least in part, on a selection ratio for the partial search term and the first set of categorized completions; determining a highest second selection ratio for the second set of categorized completions associated with the second category wherein the highest second selection ratio is greater than a second threshold value based, at least in part, on a selection ratio for the partial search term and the second set of categorized completions; ranking the highest first selection ratio and the highest second selection ratio; determining an order of each category in the set of categories based, in part, on ranking the highest first selection ratio and the highest second selection ratio; ordering the first plurality of predicted completions based, at least in part, on a position, in the order, of each category that is associated with each predicted completion in the first plurality of predicted completions; sending, to the client computer, the first plurality of predicted completions and data identifying the first set of categorized completions from the first plurality of predicted completions and the second set of categorized completions from the first plurality of predicted completions; wherein the method is performed by one or more computers.