ei ... vaan

In Finnish, vaan has several distinct roles that are essential to become proficient in.

1. The Corrective Function ('But Rather')
Use vaan when the first part of the sentence is negated and the second part provides the correct information. Note that if the second clause just adds contrasting information rather than replacing the first, use mutta instead.
Example: Hän ei ole suomalainen, vaan ruotsalainen. (He is not Finnish, but [rather] Swedish.) vs. Hän ei ole suomalainen, mutta hän puhuu suomea. (He is not Finnish, but he speaks Finnish.)

2. Not Only... But Also
A common formal structure is ei ainoastaan... vaan myös. This is used to add information rather than correct it.
Example: Hän ei puhu ainoastaan suomea vaan myös englantia. (He speaks not only Finnish, but also English.)

3. The Encouragement Particle (Spoken/Informal)
In positive sentences, especially with the singular imperative, vaan acts as a particle meaning 'go ahead' or 'just'. This is a spoken/informal feature replacing the standard vain.
Example: Tule vaan sisään! (Just come on in! / Go ahead and come in!)

4. The Warning Particle (Spoken/Informal)
In negative imperative sentences, vaan acts as a strong warning or intensifier, meaning 'don't you dare' or 'make sure you don't'. This is also a spoken/informal feature replacing vain.
Example: Älä vaan putoa! (Don't you dare fall! / Make sure you don't fall!)

5. Punctuation Rules
According to the modern standard (since 1969), a comma is generally omitted before vaan when it connects individual words or phrases (e.g., Ei teetä vaan kahvia). However, the older practice of always using a comma before vaan is still officially accepted and widely used. A comma is required if vaan connects two independent clauses that both have their own subjects and verbs.

6. Spoken Finnish Nuance
In spoken Finnish, vaan is frequently used to mean 'only' (e.g., Se maksaa vaan euron). In standard written Finnish, use vain for 'only'. Additionally, spoken Finnish often uses vaan to form indefinite pronouns meaning 'any' (e.g., mikä vaan, kuka vaan) instead of the standard mikä tahansa or kuka tahansa.

7. Sentence-initial 'Vaan' (Literary/Narrative)
In literary or narrative contexts, sentences can start with Vaan to indicate a sudden shift or contrast, similar to 'But' or 'Yet'.
Example: Vaan kuinkas sitten kävikään? (But how did it turn out then?)

8. Standalone 'Ei vaan' (Spoken)
In spoken Finnish, Ei vaan is often used as a standalone phrase to correct oneself or to say 'No, wait' or 'Just kidding'.
Example: Se on tiistaina. Ei vaan, keskiviikkona! (It's on Tuesday. No wait, Wednesday!)

Match the Negative Verb to the Subject
The label ei ... vaan uses the third-person form as a shorthand. Conjugate the negative verb: En juo teetä vaan kahvia, Emme puhu vain suomea vaan myös ruotsia. The main verb uses its connegative form after en/et/ei/emme/ette/eivät; the affirmative verb can instead appear in a separate following clause.