Learn Hardcore Finnish: Minulta loppuu aika, joten vastaan myöhemmin. - I am running out of time, so I will answer later.

Minulta is the ablative case of minä (minulta = from me / off me). Finnish often uses the ablative with verbs like loppua (to run out, to come to an end) to express that something “runs out” from someone’s possession/resources.

So the structure is literally like: Time runs out (from me) → idiomatically: I’m running out of time.

Why is the verb loppuu in 3rd person singular, not “I run out” in 1st person?

Because the grammatical subject is aika (time), not minä.

aika = subject → loppuu = 3rd person singular (it ends / it runs out)
minulta indicates whose “resource” is being depleted.

So it’s “time runs out on me” rather than “I run out time.”

Why is aika in the basic form (nominative)? Shouldn’t it be partitive like aikaa?

With loppua, the thing that runs out is typically the subject, so it’s usually nominative:

aika loppuu = time runs out

Partitive (aikaa) is more common in different constructions, for example:

Minulla ei ole aikaa. = I don’t have time.

Both talk about “not enough time,” but the grammar is different.

Is Minulta loppuu aika a normal/idiomatic way to say this?

Yes, it’s natural. It specifically highlights that your time is running out (you’re about to have no time left). You’ll also hear close variants like:

Aika loppuu. = Time is running out. (more general)
Minulla loppuu aika. = also used; minulta can feel a bit more like “it’s slipping away from me.”

What does joten mean, and is it interchangeable with niin?

joten means so / therefore, introducing a consequence:

…, joten … = …, so …

It’s often interchangeable with niin in casual speech, but joten is very straightforward as a “therefore”-connector. The comma before it is standard when it connects two clauses.

Does vastaan mean “I answer” or “against”? I’ve seen vastaan used as “against.”

Here vastaan is the verb vastata conjugated in 1st person singular present: (minä) vastaan = I answer / I reply.

You’re also right that vastaan can be a different word: a postposition meaning against / towards (e.g., seinää vastaan = against the wall). Context tells you which one it is.

Why is vastaan in the present tense if the meaning is “I’ll answer later”?

Finnish often uses the present tense for near-future plans when the time is made clear by an adverb like myöhemmin (later). So:

vastaan myöhemmin = literally I answer later → naturally I’ll reply later.

If you want to emphasize intention, you can also add something like aion:

Aion vastata myöhemmin. = I intend to reply later.

What’s the difference between myöhemmin and myöhemmin tänään / myöhemmin sitten?

myöhemmin = later (general; context decides how much later)
myöhemmin tänään = later today (more specific)
myöhemmin sitten can sound more conversational, like later on then, often reacting to what someone else said.

In your sentence, plain myöhemmin is a normal, neutral choice.

Could I drop minulta and just say Loppuu aika, joten vastaan myöhemmin?

You can, but it changes the feel:

Minulta loppuu aika clearly means I’m running out of time (personally).
Aika loppuu is more general (time is running out), and without minulta it may sound like a broader statement unless context makes it obviously about you.

So keeping minulta is usually best when you’re explaining why you have to stop.

How would I negate this sentence?

You’d typically negate each clause as needed, for example:

Minulta ei lopu aika, joten vastaan nyt. = I’m not running out of time, so I’ll answer now.

If you want to say you can’t answer now (rather than negating “running out”), a more natural approach is often:

Minulla ei ole nyt aikaa, joten vastaan myöhemmin. = I don’t have time now, so I’ll reply later.