What is called "lexeme" in rule-based natural language processing is not equal to what is called lexeme in linguistics. What is called "lexeme" in rule-based natural language processing can be equal to the linguistic equivalent only in analytic languages, such as English, but not in highly synthetic languages, such as fusional languages. What is called a lexeme in rule-based natural language processing is more similar to what is called a word in linguistics (not to be confused with a word in computer architecture), although in some cases it may be more similar to a morpheme.