The distinction might be easier to see with a less complex word than indexicality. Consider instead the following two sentences:
- “The adjective variable means that something changes.”
- “The noun variability means ‘the way that something changes’.”
The adjective form is just a simple statement of fact. “The weather is variable.” It changes.
Variability encompasses all possibilities of how something might vary. There is high-variability, low-variability, even zero-variability. Things might vary frequently or only rarely.
Indexicality is like that.
The word yesterday is indexical. It depends on the context it is written and the context it is read. Ditto with words like I and nearby.
Every word has some degree of indexicality — but that degree might be zero, or at least close.
(I tried to come up with a zero-indexicality word, without success. Platinum? No, in the music industry, platinum means something different than it does in the jewelry industry. Jupiter? Nope, mythology versus astronomy. Hey, maybe astronomy...)
Anyway, that is the difference made by omitting “the way”.