IBM Watson Natural Language Understanding (NLU) is a natural language processing service from IBM, offered within the IBM Cloud. Natural language processing (NLP) is software that reads human language and turns it into structured data. NLU is an API that uses deep learning to extract meaning and metadata from unstructured text, such as web pages or documents.
A program sends text to the API and asks for one or more features. The answer lists keywords; entities such as people, places and events; categories from a five-level hierarchy; concepts that the text implies without naming them; sentiment (positive, negative or neutral) and emotions such as joy or anger, for the whole document or for chosen phrases; relations; and semantic roles, which split sentences into subject, action and object. Users can also train custom models for their own labels, entities and relations.
NLU runs as a managed IBM Cloud service or self-hosted. Use is billed per NLU item: a free Lite plan covers a monthly quota, and the Standard plan is pay per use.