Learn Hardcore Icelandic: Þetta er alveg nóg.

Þetta: the first letter Þ/þ is the unvoiced TH of English “thing.” The double tt is pre‑aspirated, so you hear a little h before the t: roughly “THEH-hta.” IPA: [ˈθɛhta].
er: “ehr.” IPA: [ɛr].
alveg: “AL-vehg.” The final g is a soft fricative [ɣ] for many speakers; some devoice it to [k]. IPA: [ˈalvɛɣ] ~ [ˈalvɛk].
nóg: long “o” like English “no,” longer: “NOH-g,” with a soft final g [ɣ] (often sounding close to “k”). IPA: [nouːɣ] ~ [nouːk]. Primary stress is on the first syllable of each content word: ÞET-ta … AL-veg … NÓG.

What does each word mean literally?

Þetta = this (neuter singular pronoun)
er = is (3rd person singular of vera, “to be”)
alveg = completely, totally; also “quite” in many contexts
nóg = enough

What nuance does alveg add here?

alveg intensifies the statement. Þetta er alveg nóg means “This is completely/quite enough,” suggesting sufficiency with emphasis. Depending on tone, it can be neutral (“that’s perfectly sufficient”) or firm (“that’s quite enough”).

Do I need to include alveg?

No. Þetta er nóg already means “This is enough.” Adding alveg strengthens it: “This is absolutely/quite enough.” You can also soften or tweak the tone with other adverbs:

Þetta er bara nóg. = This is just enough.
Þetta er meira en nóg. = This is more than enough.

Why is it nóg and not nógt here?

Two patterns exist:

As a stand‑alone predicate or quantity word, Icelandic idiomatically uses nóg: (Þetta/Það) er nóg.
When modifying a neuter noun attributively, you use the neuter form with -t: nógt pláss (“enough space”). So your sentence uses the fixed predicative pattern with nóg.

Is nóg an adjective or an adverb here?

Functionally, it behaves like a quantity word (“enough”), much like an adverb. Historically it relates to the adjective nógur, but in predicates like Það er nóg / Þetta er nóg, speakers use the indeclinable nóg. When it modifies adjectives/adverbs, the form is nógu (see next question).

How do I say “big enough,” “fast enough,” etc.?

Use nógu before adjectives/adverbs:

nógu stórt = big enough (neuter target)
nógu hratt = fast enough
nógu gott = good enough
nógu mikið = enough (of quantity, “sufficiently much”)

How do I say “enough of X” and “enough for someone”?

“Enough of X”: nóg af + dative
- Það er nóg af mat. = There’s plenty of food.
- Ég á nóg af peningum. = I have enough money.
“Enough for [person]”: nóg fyrir + accusative
- Þetta er nóg fyrir mig/okkur. = This is enough for me/us.

Can I use það instead of þetta?

Often, yes. Það er (alveg) nóg is common as a general statement (“That/it is enough”). Þetta points more directly to something present or just mentioned (“this here/this amount”), while það can be more general or refer to something less immediate.

Is the word order fixed? Could I say “Þetta er nóg alveg”?

Keep alveg directly before nóg: Þetta er alveg nóg. “Þetta er nóg alveg” is unidiomatic. You might hear fronting for emphasis (e.g., Alveg nóg er þetta), but the neutral, natural order is the one you have.

Is this sentence polite or could it sound curt?

It’s neutral. Context and tone decide the feel. Additions like takk help in service contexts:

Þetta er alveg nóg, takk. = That’s quite enough, thanks.

How do I negate it?

Þetta er ekki nóg. = This is not enough.
Þetta er ekki alveg nóg. = This is not quite enough.
Stronger: Þetta er alls ekki nóg. = This is by no means enough.

Are there close synonyms?

Yes:

Þetta dugar (alveg). = This suffices (fully).
More formal/literary: Þetta nægir. = This is sufficient.
Adjectival alternative (more formal): Þetta er nægilegt. = This is sufficient/adequate.

How would I say it in other tenses?

Past: Þetta var alveg nóg. = This was quite enough.
Future: Þetta verður alveg nóg. = This will be quite enough.
Conditional: Þetta væri alveg nóg. = This would be quite enough.

Why is there no article (“a/the”)?

Icelandic has no separate indefinite article, and the definite article is a suffix on nouns (e.g., bókin = “the book”). Here, þetta (“this”) already specifies the reference, so no article is needed.

Could I say Þessi er alveg nóg?

Not in this bare form. Þessi is a demonstrative that normally comes with a noun (or stands for a specific “this one” with an understood gender/number). You’d say, for example:

Pointing at a portion (neuter noun): Þetta er nógt magn. = This is an enough quantity.
Referring to a specific item with its noun: Þessi skammtur er alveg nógur. = This portion is quite enough. For a general “this (amount) is enough,” stick with Þetta er (alveg) nóg.

Any quick tips about the sounds in this sentence?

Þ/þ is the unvoiced TH of “thing,” never like English “t” or “s.”
Double tt is pre‑aspirated: think a brief “h” before the t.
Final g (in alveg, nóg) is usually a soft fricative [ɣ] and may devoice toward [k]. Don’t make it a hard English “g.”