T9 (predictive text)

Text on 9 keys ( in German: "Text on 9 keys " ), short- T9 is a patented system for facilitating text entry on a mobile phone. It was invented by the Americans Clifford A. Kushler, Dale Grover, Martin T. King and Cheryl A. Grunbock and of the company Tegic Communications Inc. (USA ), a subsidiary of Time Warner AOL LLC, launched in January 1998. The introduction in Germany was the first time in 1999 with the delivery of the mobile phone type Nokia 3210. In June 2007, Nuance Communications Inc. has accepted Tegic.


Modern phones have a 12- keypad with the digits 0 to 9 and two control functions for dialing. For additional text entry are the " 2 " key to assigned "9" three to four letters of the Latin alphabet. In the normal entry of text on this keyboard key according to the position of the desired letter has to be actuated once or more.

To reduce the multiple key press, during the operation with the "T9 " system software controlled a word - proposal from a built-in dictionary appears on the phone display and offered for adoption.

The T9 system makes use of the fact that every episode pressing the keys 2 to 9, only a small number of meaningful words of a particular language, even longer sequences of numbers often correspond to exactly one word. Furthermore, only a few are commonly used in several possible combinations of letters per key sequence in the language.

The input of a word is thus by each letter the corresponding number button is pressed more than once. After each new input, the software from the dictionary suggests, if possible, the appropriate word with the highest frequency of use before. With several options you can scroll through all matching words with one of the control buttons. If a word is not contained in the dictionary ( eg rare proper names), so this can be added to the dictionary.

For example, the word house written with the key sequence " 4-2-8-7 ": the mobile phone software first offers at the 4 button, the "I" ( or " i" ), since the letters G and H significantly be used less individually. If then the other keys this episode depressed, arise successively " Ha ", " hat", and finally " home ".


The main advantage is that in most cases fewer keystrokes are needed. Moreover, the problem does not apply if two successively used letters are on the same key: Usually must be inserted between the input of the individual letters either a short wait or a confirmation button to be pressed.

In order, for example, the word " Hello " to write, you have to press a button and without T9 twelve times take a longer break once or press the enter key:

  • 4 4 2 5 5 5 Pause / Confirmation 5 5 5 6 6 6

With T9 rich five keystrokes:

  • 4 2 5 5 6


T9 is for texts with many terms that are not part of the normal vocabulary, such as proper names, geographical indications and dialect, not suitable because they are not included in the T9 dictionary. In addition, the vocabulary of a mobile phone is sometimes very small, for example, are the Nokia 6230i among other things, the words " brush " and " toothbrush " unknown.

In addition, it can only be used for languages ​​which are standardized and for which there is a dictionary. So T9 is hardly used in German-speaking Switzerland, since the Swiss German, has the usual SMS language in German-speaking Switzerland, no standardized written language.

Another weakness of digits to which two matching sequences of letters exist, both of which are used equally often and require appropriate corrections or leaves with the control button. Examples:

Some users dealing with the T9 system is perceived as too cumbersome, because it requires eg frequent Scroll through the options or adding non-existent terms in the dictionary. Specially experienced users can enter texts sometimes faster without T9, despite the higher number of key presses.


The German language version was " denazification ". In its original version words such as people and Nazi were displayed as the first alternative, since it from the Internet search company a higher utilization rate than had the words full and Maxi. Meanwhile, the sort order is changed, however, and some words, such as the Jewish question were deleted from the T9 dictionary.

T9 words corrected frequently by so changed by the changed word, the overall context of dialogue and strange new meanings emerge. An innovative devices (smartphones ) T9 keyboard has been converted into a digital QWERTY layout and the AutoText added to help you write, so that it can also occur there strange auto completion.