In computational linguistics, annotation means adding structured labels to text data so machines can learn from it.In computational linguistics, annotation means adding structured labels to text data so machines can learn from it-Text annotation is the process of adding information to a written text in order to explain, analyze, interpret, or categorize it. Annotations can be simple notes in the margin or complex structured labels used in research and artificial intelligence. The purpose of annotation depends on the context: learning, research, linguistic analysis, or machine learning.