system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:If Haiku are Japanese, why are they 7:5:7 syllables in English?

I understand it's kind of a weird question, and may not make sense at all, but it's really bugging me. I dont understand. When we translate a Haiku into English, do we change words until it's 7:5:7? Is that not a rule in actual Japanese Haiku?
gpt
It's just a way to adapt their poetry form into our language. 

It should also be noted that the original Japanese form is NOT 5/7/5 syllables.  It is 5/7/5 moras. A mora is a unit of length defined as the vowel and anything following it.  A long vowel counts as two morae. English speakers often find it strange, because our language ignores morae.  Here's an example to demonstrate:

edo no ame  
nan goku nonda   
hototogisu  
~Issa

"How many gallons  
of Edo's rain did you drink?  
cuckoo"  

Notice how the second line has only five syllables? It still fits the meter because "nan" has two morae (a and n), and "nonda" has three (o, n, and a). Japanese poetry doesn't care about syllables, it cares about moras.  Oftentimes moras line up with syllables, because CVC syllables are somewhat uncommon in Japanese, but it's a crucial distinction.