system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are silent letters a thing?
gpt
Different silent letters are there for different reasons.

Some are there because they didn't used to be silent. The K in knife and knight used to be pronounced, and the gh in knight used to be pronounced like the ch in loch or the h in Ahmed.

In other cases, a silent letter was deliberately added to be more like the Latin word it evolved from. The word debt comes from the French *dette*, and used to be spelled dette in English too, but we started spelling it debt because in Latin it was *debitum*.