What Does Nano Mean Now?

[hydra]

In science it means one/one-billionth.
It was adopted by the ancient Greeks as a prefix meaning dwarf.
15-20 years ago, we became enthusiastic about tiny meticulously aquascaped aquariums under 5 gallons called nano tanks.
Now I keep seeing things like "20g Nano for Sale", "WANTED: 30g Nano Reef Tank", etc,...
For centuries, nano has meant tiny. So what the crap is a 20-30 gallon nano?

[mnemenoi]

Nano usually refers to a reef system under 30 gallons or planted tank under 20 gallons. Pico tanks are in the 10 gallon and under size.

[mistahoo]

For a reef tank 30 gallons and under is puny as most run larger setups since larger setups usually have much more stability when it comes to water parameters.

[ptran]

Nano to me is anything less than 10 gallon.

[hydra]

So they're calling nanos "picos" now?
I did not get that memo.
Thanks everyone. Good to know.
Now to figure out when everybody started thinking "hydro" means potent. :P