What the definition says
On this page12
Subparagraph (A), the device
"means any electronic device that, through an aerosolized solution, delivers nicotine, flavor, or any other substance to the user inhaling from the device".
Three alternatives in that list
Nicotine, flavor, or any other substance. So the text does not turn on nicotine being present in the thing delivered.
Which is worth noticing and not concluding from
How that applies to a particular product is a determination. This property quotes the text and stops.
Subparagraph (B), the examples
An e-cigarette, an e-hookah, an e-cigar, a vape pen, an advanced refillable personal vaporizer and an electronic pipe. Six named articles.
And then (vii), the catch-all
"any component, liquid, part, or accessory of a device described in subparagraph (A), without regard to whether the component, liquid, part, or accessory is sold separately from the device".
Four nouns, all of them broad
Component, liquid, part, accessory. A liquid is named explicitly, which is how an e-liquid sold with no device attached is reached.
Subparagraph (C), the exception
A product "approved by the Food and Drug Administration for-- (I) sale as a tobacco cessation product; or (II) any other therapeutic purpose" and "marketed and sold solely for a purpose described in clause (i)".
Both limbs are required
Approved for one of those purposes, and marketed and sold solely for it. An approval without the solely is not enough.
Which is a narrow door
And it is the only exception stated in the paragraph. Everything else in the definition is inclusive.
The named examples are not a closed list
Six articles are named and then the catch-all follows, which means the list illustrates rather than limits. A device not on the list is not outside the definition for that reason.
None of this is a packaging rule
There is no size, material, closure or label requirement anywhere in it. The definition decides what something is and the consequence lives in a different title.