Hold your palm a few centimetres from your mouth and say pan, then say fan. Your hand just answered the question. This is the one pair here you can check without using your ears.
A Stream Against an Explosion
These two sounds are built completely differently, which is why this pair becomes reliable fairly quickly once you know what to listen for.
f in fan
Top teeth rest on the bottom lip, leaving a narrow gap. Air flows through it continuously and can keep going as long as you have breath. Nothing ever fully closes.
p in pan
Both lips seal completely. Pressure builds behind them with no escape, then releases all at once in a single burst. It cannot be stretched — it is one event, then silence.
Where the Substitution Comes From
Neither Korean nor Japanese historically carried an /f/. Japanese approximates it with a softer sound made using both lips, and loanwords entering Korean routinely swap in /p/ instead. So hearing fan as pan is the nearest native category doing exactly its job. The useful consequence is that your production and your perception are usually stuck together: training one tends to move the other, which is why a physical check beats a careful one here.
You Can Feel This One on Your Hand
Do it slowly and the two are unmistakable. With pan, a distinct puff of air hits your hand at the very start: one sharp burst, then nothing. With fan, the airflow is weaker and steadier and lasts as long as you hold the sound, with no punch at the front. Almost no other pair in English gives you feedback this physical. If you are trying to train production alongside perception, this is the pair to start with, because your hand tells you whether you got it right without needing anyone to confirm.
Same Lips, Different Question
- van / fan
Keeps the f but changes what it is competing against — voicing instead of lip closure.
- bear / pear
Two lip-closing sounds against each other, with only voicing between them.