What is t9 dialing?

T9 dialing is a predictive text input method used on mobile phones to input texts and numbers by pressing a numeric keypad. It works by using an algorithm to predict the word being entered, based on the sequence of key presses. This method was first introduced by Tegic Communications in 1995 as a faster and more efficient alternative to traditional multi-tap key input. T9 supports several languages and is still used on phones today, although it has largely been replaced by touch screen technology.