T9 (predictive text)

T9, which stands for Text on 9 keys, is a USA-patentedpredictive text technology for mobile phones (specifically those that contain a 3x4 numeric keypad), originally developed by Tegic Communications, now part of Nuance Communications.

T9 was used on phones from Verizon Wireless, NEC, Nokia, Samsung Electronics, Siemens, Sony Ericsson, Sanyo, Sagem and others. It was also used by Texas Instruments PDA Avigo during the late 1990s. Its main competitors are iTap created by Motorola, SureType created by RIM, Eatoni's LetterWise and WordWise, and Intelab's Tauto.

T9's objective is to make it easier to type text messages. It allows words to be entered by a single keypress for each letter, as opposed to the multi-tap approach used in conventional mobile phone text entry, in which several letters are associated with each key, and selecting one letter often requires multiple keypresses.

It combines the groups of letters on each phone key with a fast-access dictionary of words. It looks up in the dictionary all words corresponding to the sequence of keypresses and orders them by frequency of use. As T9 "gains familiarity" with the words and phrases the user commonly uses, it speeds up the process by offering the most frequently used words first and then lets the user access other choices with one or more presses of a predefined "Next" key.

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