# What is the exact definition of a dictionary in the concept of linear algebra and computer science?

I am reading this paper for my master thesis and trying to understand every concept in it. The following sentence confuses me as to what is the exact definition of a dictionary in this concept except for the fact that it holds the atoms as its columns?

Recall we refer to the columns of the matrix $A$ as atoms that are later used as building blocks in the construction of $b$. Such a matrix that holds the atoms as its columnsis referred to as a dictionary[...].

• not sure where this use originated but maybe in LSA type apps? take a look at bag of words model – vzn Sep 9 '15 at 15:10