Learn Hardcore Icelandic: Við tölum daglega saman á netinu.

So with við (we), the correct form is tölum, not tala.
The vowel change a → ö plus the ending -um is just how this verb behaves in the 1st person plural.

What exactly does daglega mean, and why isn’t it daglegur?

Daglega is an adverb meaning daily / every day.

daglegur – daily, as an adjective (describing a noun), e.g.:
- daglegur matur – daily food
- dagleg vinna – daily work
daglega – daily, as an adverb (describing a verb), e.g.:
- Við tölum daglega – We talk daily.

In your sentence, daglega describes how often you talk, so it must be an adverb, not an adjective. Adverbs like daglega don’t change for gender, number, or case.

What does saman add to the meaning? Could I leave it out?

Saman means together.

In tala saman, it gives a reciprocal meaning: talk with each other rather than just “speak” in general.

Við tölum daglega á netinu.
Can mean: we (each) speak (maybe not clearly to each other).
Við tölum daglega saman á netinu.
Clearer: we talk to each other daily online.

In real usage, tala saman is a very common fixed combination for “talk together / talk to each other,” so saman is natural and idiomatic here.

You can omit saman, and the sentence is still correct, but tala saman better emphasizes the idea that you two are specifically talking with each other.

Why is it á netinu and not á netið or just á neti?

This is about prepositions, case, and definiteness.

Preposition “á” (on/at/in)
- With dative = location (where?):
  - á netinu – on the internet (where the talking happens)
- With accusative = motion (to where?):
  - á netið – onto the internet / to the internet
Since the sentence describes where you regularly talk (a location, not a direction of movement), á takes the dative.
The noun “net” (neuter, “net / the internet”)
Singular forms:
- Nom: net
- Acc: net
- Dat: neti
- Gen: nets
Definite singular (with “the”):
- Nom: netið – the net
- Acc: netið
- Dat: netinu
- Gen: netsins
So á + netinu (dative definite) literally is on the net / on the internet.
Why not á neti (indefinite)?
You could say it in some contexts, but just like English prefers on the internet, Icelandic usually prefers the definite form here: á netinu.

What’s the difference between á netinu and á internetinu or á netið?

á netinu – on the internet
Most common, everyday expression. Equivalent to English online / on the internet.
á internetinu – on the internet
Same meaning; just uses the full word internetið instead of netið. Slightly more formal or explicit, but both are fine.
á netið – onto the internet / to the internet
Accusative = motion towards the internet, e.g.:
- Ég set mynd á netið. – I upload a picture to the internet. It does not mean “on the internet” as a location where the action is happening over time; that needs the dative: á netinu.

Can the word order change? For example, can I say Við tölum saman daglega á netinu?

Yes, Icelandic word order is somewhat flexible, and several variants are natural:

Við tölum daglega saman á netinu. (your original)
Við tölum saman daglega á netinu. – also natural, maybe a tiny bit more common.
Við tölum daglega á netinu saman. – possible, but saman feels a bit “tacked on” at the end.
Daglega tölum við saman á netinu. – emphasizes daglega (daily).

Some guidelines:

The finite verb (here: tölum) normally stays in the second position in statements.
Saman usually comes close to the verb it modifies, often right after it: tölum saman.
Time adverbs like daglega can move around fairly freely, but typically appear near the verb too.

So Við tölum saman daglega á netinu is perfectly fine.

Could I drop við and just say Tölum daglega saman á netinu?

If you drop við, you change the meaning.

Við tölum daglega saman á netinu.
Statement: We talk together online every day.
Tölum daglega saman á netinu.
Now it reads as an imperative:
Let’s talk together online every day.

In Icelandic, unlike in Spanish or Italian, you normally keep the subject pronoun (ég, þú, við, þið, etc.) in everyday speech and writing. Dropping við here does not give you a neutral statement; it sounds like a suggestion or command: Let’s talk...

Is tala closer to “speak”, “talk”, or “chat”? Are there other common verbs here?

Tala covers both speak and talk quite broadly.

In this sentence, Við tölum daglega saman á netinu can be understood as:

We talk together online every day.
We speak together online every day.

Other useful verbs:

spjalla – to chat (more informal, conversational)
- Við spjöllum saman daglega á netinu. – We chat together online every day.
ræða (við einhvern) – to discuss, to talk over something (more about content or discussion)
- Við ræðum saman daglega á netinu. – We discuss things together online every day.

But tala saman is the most neutral and common choice for general “talk to each other”.

How would I make this sentence negative, or turn it into a question?

1. Negation

Use ekki after the finite verb:

Við tölum ekki daglega saman á netinu.
We don’t talk together online every day.

You can move daglega a bit, but keep ekki right after tölum:

Við tölum ekki saman daglega á netinu.

2. Yes/no question

Icelandic usually forms yes/no questions by putting the verb first:

Tölum við daglega saman á netinu?
Do we talk together online every day?

No do-support like English; you just invert tölum and við.

How would I say “We are talking together online right now”? Is there a special continuous form?

Icelandic has one basic present tense, but it also uses vera að + infinitive to express something like the English present continuous.

For We are talking together online right now, you can say:

Við erum að tala saman á netinu núna.

Breakdown:

við erum – we are
að tala – (to) talk / talking
saman – together
á netinu – online / on the internet
núna – now

Your original sentence Við tölum daglega saman á netinu is more habitual (we do this regularly).
The vera að construction emphasizes an action in progress right now.

How do you pronounce við, tölum, and á?

Very briefly:

við
- The ð is a soft, voiced th sound like in this, not like in think.
- Roughly like English vith (with a soft th).
tölum
- ö is like the German ö, or like saying English uh but with rounded lips.
- Stress is on the first syllable: TÖ-lum.
á
- A long sound, similar to English ow in cow, but held as one long vowel, not a clear diphthong.
- Always stressed when it’s its own word.

Also, in Icelandic, stress is almost always on the first syllable of the word:
VIð tölum DAGlega SAm-an á NE-tinu.

What forms do við and net have in other cases?

1. The pronoun “við” (we)

Plural of the 1st person:

Nominative: við – we (subject)
Accusative: okkur – us (direct object)
Dative: okkur – us (indirect object)
Genitive: okkar – our / of us

In your sentence, við is in the nominative as the subject.

2. The noun “net” (neuter)

Singular:

Nom: net – (a) net / internet
Acc: net
Dat: neti
Gen: nets

Definite singular:

Nom: netið
Acc: netið
Dat: netinu
Gen: netsins

Your phrase á netinu uses the dative definite: “on the internet”.

How would the sentence change with other subjects like “I” or “they”?

Keeping the rest of the sentence the same:

Ég tala daglega saman á netinu.
I talk daily together online.
(More natural: Ég tala daglega við hana/hann á netinu. – I talk to her/him daily online, i.e. say who you talk to.)
Þú talar daglega saman á netinu.
You (sing.) talk daily together online.
(Again, usually: Þú talar daglega við hann/hana á netinu.)
Hann/Hún talar daglega saman á netinu.
He/She talks daily together online.
(Typically: Hann/Hún talar daglega við hana/hann á netinu.)
Þeir / Þær / Þau tala daglega saman á netinu.
They talk together online every day.

The important thing for conjugation is:

við tölum – we talk
þeir/þær/þau tala – they talk
ég tala – I talk
þú talar, hann/hún talar – you (sing.), he, she talks

So the verb ending changes with the subject pronoun.