* Morphemes are the smallest meaningful units of language. Even words that appear to be single units often contain a single morpheme that acts as both the root and the whole word.
* Every word must have a root morpheme. This is the core of the word's meaning. For example, the word "cat" has a single morpheme that serves as both the root and the whole word.
Examples:
* "run" - One morpheme (root)
* "unbreakable" - Three morphemes (un- + break + -able)
Conclusion:
Even the simplest words in English have at least one morpheme. There's no such thing as a word with zero morphemes.