Also I intuitively get that a sonnet is "shorter" than an opus (although Fable is less clear) - I have no idea what i'm even supposed to be comparing with google elements... Atomic number? I know hydrogen is the lowest and i guess argon is bigger than carbon but am I expected to know that? Or is it by weight? Argon's a gas so it's lighter than Carbon?

The sol/terra/astra, haiku/sonnet/opus clicked without needing to be explained

A mythos is longer than an opus.

A fable is a tame mythos.