对于给定的一篇文章，请输出前20个最常用的单词和出现次数。


"Natural language processing (NLP) is a subfield of computer science, information engineering, and artificial intelligence concerned with the interactions between computers and human languages, in particular how to program computers to process and analyze large amounts of natural language data."
Natural: 1
language: 2
processing: 1
(NLP): 1
is: 1
a: 2
subfield: 1
of: 2
computer: 1
science,: 1
information: 1
engineering,: 1
and: 3
artificial: 1
intelligence: 1
concerned: 1
with: 2
the: 3
interactions: 1
between: 1.