Here's why:
* Lexical innovation refers to the creation of new words or meanings.
* Portmanteau words are formed by combining parts of two or more existing words.
Therefore, portmanteaus are a specific type of lexical innovation, alongside other methods like:
* Blends: Combining sounds or syllables (like "smog" from "smoke" and "fog")
* Acronyms: Combining initial letters (like "NASA" from "National Aeronautics and Space Administration")
* Coinages: Inventing entirely new words (like "blog")
So, while "portmanteau word" describes a specific word formation technique, it falls under the broader category of lexical innovation, which encompasses all ways of creating new vocabulary.