Even that's not unambiguous. Singular verbs in English end in -s, introducing ambiguity as to if "runs" is a verb or noun. Sure, you can figure out that the verb that ends in s in "he runs" is a verb based on the grammar (that properly constructed sentences have both a subject and a predicate, and less often are composed of only two nouns (baring implicit sentence components that English is prone to encourage), but that requires more context than recognizing nouns based solely on "the usual verbs are noun-ified by adding an -s".