system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do some words need two of the same letter in a row to make the same sound (like the 'n' in 'bunny') and how do I remember when I need two letters instead of one? Asked by an actual five year old.
gpt
One way is to say it slowly. If the sound is in both syllables, or crosses the syllable, it's probably a double letter.

"Bunny" is "bun ny". "Letter" is "let ter". "slowly" is "slow ly". "Syllable" is "syl la ble".

It's not a perfect rule, but every rule in spelling has exceptions.