The entire difference here is teeth. One sound uses them and the other never does, which makes this pair visible from across a room.
The Whole Answer Is Teeth
For v, your top teeth make contact with your bottom lip and hold there while air pushes through the gap. For w, nothing touches anything at all — the lips round and come close together, then immediately glide apart into the vowel. That is the entire difference, and it is unusually clean for a pair this hard: one sound uses teeth, the other never does. There is no subtle tongue position to master and no timing to get right.
What the Research Actually Found
Korean has no native /v/, and the sounds sitting closest to it in the mouth are right next to /w/. Korean-English pronunciation research documents both perception and production of this pair drifting toward one merged sound, which is a useful thing to know: it means the confusion is systematic rather than random. Systematic problems respond well to a single reliable cue, and for this pair that cue is whether teeth were involved at all.
This One You Can See
Because the contact is at the front of the mouth, it is visible from across a room and obvious on screen. If you are watching a show or on a video call, look at whether the top teeth land on the bottom lip. On w they never do — the lips round outward, away from the teeth, almost like the start of a whistle. Being able to check with your eyes matters more than it sounds, because it lets you confirm what you heard and slowly build the sound category your first language didn't hand you.
Two Sentences That Both Make Sense
This pair turns up constantly in place names, food and drink, and small talk about the weather:
On a tour of a vineyard
The vine is doing well this year.
The wine is doing well this year.
Both are true, both are things a guide would say, and nothing else in the sentence separates them. These are the moments where the distinction has to come from your ear alone.
Follow the V Somewhere Else
- van / fan
Keeps the teeth-on-lip contact and changes only whether your voice is switched on.
- berry / very
The third direction /v/ drifts — this time toward b.