Learn Hardcore Icelandic: Rafhlaðan virkar núna.

The ending -an is the suffixed definite article for feminine nouns ending in -a. It corresponds to English “the.” The base word is rafhlaða (battery). When you add the article -in to a noun ending in -a, the i drops, giving -an:

rafhlaða + -in → rafhlaðan = “the battery”
Without it: rafhlaða = “a battery”

What gender is rafhlaða, and which pronoun should I use for it?

Rafhlaða is feminine. Refer back to it with hún (she/it). Example: Hún virkar núna.

How is virkar formed? What are the present-tense forms of virka?

Virka is a regular weak verb. Present tense:

ég virka
þú virkar
hann/hún/það virkar
við virkum
þið virkið
þeir/þær/þau virka

Past (for reference): ég virkaði, hún virkaði, við virkuðum, etc. Example: Rafhlaðan virkaði (The battery worked).

Can I say “is working now” in Icelandic, like “Rafhlaðan er að virka núna”?

Normally no. For states like “to function,” Icelandic uses the simple present: Rafhlaðan virkar núna.
If you mean “has started to work,” you can say:

Hún er farin að virka.
Hún er byrjuð að virka.

Where does núna go? Are there other acceptable positions?

Neutral: Rafhlaðan virkar núna.
To emphasize the time: Núna virkar rafhlaðan.
With time-limited negation: Rafhlaðan virkar ekki núna. (“doesn’t work right now”) Avoid placing núna between subject and verb in the affirmative.

How do I negate it?

Put ekki after the verb:

Rafhlaðan virkar ekki.
With a time adverb: Rafhlaðan virkar ekki núna. For “no longer,” use ekki lengur: Rafhlaðan virkar ekki lengur.
For “still,” use enn or ennþá: Hún virkar enn (ennþá).

How do I turn it into a yes/no question?

Put the finite verb first:

Virkar rafhlaðan núna?
Answers: Já, hún virkar. / Nei, hún virkar ekki.

What exactly does virka mean here, and how is it different from vinna, ganga, or virkja?

virka = to function/work (as in not broken). Devices, systems, medicines: Tölvan virkar.
vinna = to work (do a job/labor). Not used for devices: Ég vinn á spítalanum.
ganga = to run/operate/go. Used of machines running: Vélin gengur vel (“The machine runs well”). For a battery, prefer virka.
virkja = to activate/harness (transitive): að virkja rafmagn, að virkja lykil (“activate a key”).

Any pronunciation tips for this sentence?

Primary stress on the first syllable of each word.
r is tapped/rolled.
ð in rafhlaðan sounds like the “th” in “this.”
ú in núna is like “oo” in “food.”
hl is pronounced with a voiceless l (a faint h + l sound): hla-.
Rough guide: “raf-hla-than vir-kar NOO-na” (with i in virkar like the i in “bit”).

Can I use nú instead of núna? Any difference?

Yes. Both mean “now.” Núna is the everyday neutral choice. Nú is shorter and can feel a bit more formal or rhetorical, and it’s also used as a discourse particle (“well/now”). Rafhlaðan virkar nú is fine but less conversational than Rafhlaðan virkar núna.

Is rafhlaða always the right word for “battery”?

General batteries (AA/AAA/phone): rafhlaða.
Car battery: rafgeymir.
Colloquially some say batterí, but that also means “drum kit,” so rafhlaða is safest in neutral/formal use.

What are some common inflected forms of rafhlaða I should know?

Singular:

Nominative: rafhlaða (indef), rafhlaðan (def)
Accusative: rafhlöðu
Dative: rafhlöðu
Genitive: rafhlöðu Plural:
Nominative/Accusative: rafhlöður
Dative: rafhlöðum
Definite plural (nom/acc): rafhlöðurnar

How do I say “The battery works again now” or “no longer works”?

“again now”: Rafhlaðan virkar aftur núna.
“no longer works”: Rafhlaðan virkar ekki lengur.
“still works”: Hún virkar enn/ennþá.

Why is there no separate word for “the”? How do definite articles work?

Icelandic uses suffixed definite articles:

Masculine: -inn (e.g., bíllinn = the car)
Feminine: -in (becomes -an after final -a: tölvan, rafhlaðan)
Neuter: -ið (e.g., húsið = the house)

Does virka have any other meanings I should know?

Yes. Besides “to function,” virka also means “to crochet” in crafting contexts. Context disambiguates. Don’t confuse the verb virka with the adjective virkur (“active”).

How does the verb change with a plural subject?

Third-person plural takes the form virka (no -r):

Rafhlöðurnar virka núna. (“The batteries work now.”)
Rafhlöður virka núna. (“Batteries work now.”)