1. A method for assisting in avoiding incorrect input in a portable terminal, the method comprising: identifying an input character string and, among previously registered candidate words, searching among a plurality of candidate words recommended for the input character string; calculating a similarity between the input character string and each of the searched candidate words based at least partially upon a type of keypad used to input the input character string, wherein calculating the similarity between the input character string and each of the searched candidate words comprises: identifying the keypad type; determining each cost of an insert operation, a delete operation, and a replace operation corresponding to the identified keypad type; and calculating an edit distance using the operations according to the respective cost of each of the candidate words; and providing one or more of the searched candidate words according to the calculated similarity.