A Natural Language Interface (NLI) allows users to interact with an information system via language. The user can draw on everyday vocabulary and does not have to restrict himself to special syntaxes, such as those used by search engines.
With the natural language user interface, the user can enter his input as spoken words or phrases and receive detailed information. He does not use standardized command inputs or logical operands. Due to the ambiguity of words, the spoken words or sentences can be interpreted incorrectly. To better interpret what is spoken, Natural Language Interfaces can use Automatic Speech Recognition ( ASR).
Natural Language User Interfaces are used in special search engines, where the user can enter complete sentences and receive precise search results, in computer games, where the avatars have their own characters and interact like people, or in document management.