It's no secret that a lot of words in English can function as more than one word class. Verbs like walk and drive are easily remobilized as nouns: We went for a walk, and they went for a drive. Even Latinate verbs like intercept or invite can nominalize rather promiscuously, as in FISA will allow the intercept because a warrant was obtained, or Did you get the invite?
That particular process is called nominalization. There's also verbalization, in which a word of a different class is verbed. This happens a lot with nominal stems: I friended you. They are texting each other. And older examples abound too, like We must face our problems together, or The fish will soon begin homing to their spawning habitat. Dialogue. Photograph. Table. Verbing also happen with adjectival stems: I've already emptied my pockets, or Please wash any dishes that you've dirtied. There's a famous Calvin & Hobbes cartoon whose punchline is "Verbing weirds language." You can google it yourself and I won't have to pay a licensing fee to reproduce it here.
Verbing a noun or nominalizing a verb without adding a suffix is called zero-derivation, or sometimes conversion. It's easy in English because English is largely analytic and lacks a rich inflectional system in its grammar, but it also happens in other languages. For example, in French, the verb rire 'to laugh' has become a noun: un rire 'a laugh.' The adverb bien 'well' is now used as a noun, le bien, 'the good.' The process doesn't just happen between lexical categories; functional stems can also be lexified through zero-derivation: He upped his offer. The ins and outs of the situation... And in French, le dessous, 'the under.'
Sometimes, finding an English word that is associated with multiple parts of speech is not a question of zero-derivation diachronically, but a question of historically distinct nominal and verbal forms collapsing together because they lost their inflectional differentiations over time. People in my Not Angles but Angels class – closely reading This Language, A River – have learned all about that process. This is the case with native English words like love and hate, but also with French-origin words, like block and taste. Sometimes it's hard to tell whether it's synchronic zero-derivation or a diachronic merger, as with joke or advocate.
But what about when we're dealing exclusively with function word categories, like words that can be both prepositions and functional adverbs, or words that can be both pronouns and determiners?
What about that?
That's what this post is about.