1. A correction method of a word or a character substring, the method comprising: displaying, on a screen of a device, one or more words in response to input from a user; displaying, on the screen of the device, a new character substring in response to input from the user after displaying the one or more words on the screen; calculating a correlation between character substrings of the one or more words and the new character substring based on a proximity of keys for the character substrings and keys for the new character substring on a keyboard; determining whether or not to register at least one of the character substrings of the one or more words in a correction candidate list based on the calculated correlation; receiving a correction command from the user; if only one of the character substrings is registered in the correction candidate list, replacing the character substring registered in the correction candidate list with the new character substring, in response to the correction command, such that the new character substring is displayed at a location where the character substring registered in the correction candidate list was displayed; and if two or more of the character substrings are registered in the correction candidate list, replacing a first character substring of the two or more of the character substrings displayed on the screen with the new character substring, in response to the correction command, such that the new character sub string is displayed at a location where the first character substring was displayed, and replacing a second character substring of the two or more of the character substrings displayed on the screen with the new character substring, in response to a move command, such that the new character substring is displayed at a location where the second character substring was displayed.