给定一篇英文文章和一个单词，输出该单词在文章中出现的次数。
文章：“Natural language processing (NLP) is a field of computer science, artificial intelligence and computational linguistics concerned with the interactions between computers and human (natural) languages. As such, NLP is related to the area of human–computer interaction. Many challenges in NLP involve natural language understanding, that is, enabling computers to derive meaning from human or natural language input.”
单词：language
该单词在文章中出现了 4 次。