Learn Icelandic: Halló! Er læknirinn hér?

In Icelandic, the word for 'the' (the definite article) is attached to the end of the noun instead of standing alone. The base word is læknir (doctor), and adding the masculine ending -inn makes it læknirinn (the doctor).

How do we know this is a question if there is no question word like 'hvar' or 'hvað'?

Because the verb comes first! Just like in English, you can turn a simple statement into a yes/no question by putting the verb before the subject. So, Læknirinn er hér (The doctor is here) becomes Er læknirinn hér? (Is the doctor here?).

Could I use hérna instead of hér in this sentence?

Yes, absolutely. Both hér and hérna mean 'here'. Hérna is very common in everyday spoken Icelandic, while hér is a little shorter, but they mean the exact same thing in this context.

Is Halló an appropriate greeting to use at a doctor's office?

Halló is a good, neutral greeting that works in almost any everyday situation, including walking up to a reception desk. You could also use the slightly more polite Góðan daginn (Good day) depending on the time of day.