Word substitution is designed to replace specific text that you type with preloaded word substitution entries. If you type text that can be replaced with a word substitution entry, the text changes after you press the Space key.
Your BlackBerry smartphone has built-in word substitution entries that correct common mistakes. For example, word substitution changes hte to the. You can create word substitution entries for your common typing mistakes or for abbreviations. For example, you might create a word substitution entry that replaces ttyl with talk to you later.