Countable nouns - Air Quality Index

[Scarmaker]

Hello, few days ago I came across "Air Quality Index"

We are talking about some kind of index of air quality and we can have more of them, so by that logic, this noun should be countable. However, we are talking about Air Quality Index not air quality index, meaning there is only one of it's kind and by that logic, this noun should be uncountable.

Can you help me with this?

Thx.

 

[SoothingDave]

These would be measurements of particulates, etc. in the air.

There would be measurements given daily, and given for various locations.

So you could indeed refer to Air Quality Indexes (or Indices).

"The AQI's have been very high this week."

 

[Tdol]

Also, the fact that there is only one of something doesn't make it uncountable- if there could be two, it would be countable, just singular. There's only one sun, but there could be two....

 

[Scarmaker]

Thank you.

However, someone pointed out that "AQI is a measurement, so it's an uncountable noun"

 

[SoothingDave]

Why would a measurement be uncountable?