"Each Other" and "The Others" in Icelandic

Icelandic is very precise about numbers. The words you use to say "each other" or "the other one" change completely depending on whether you are talking about two people or more than two.

"The Other" vs. "The Rest" (Annar vs. Hinn vs. Einn)

How do you distinguish items in a group? It depends on the size of the group.

The Group of Two (2)

If you have exactly two things (e.g., two students), you use Annar (the one) and Hinn (the other).

Ég á tvo bræður. Annar býr á Íslandi, en hinn býr í Danmörku. (I have two brothers. One lives in Iceland, but the other lives in Denmark.)

The Group of Many (3+)

If you have more than two things (e.g., four students), you use Einn (one) and Hinir (the others/the rest).

Ég á þrjá bræður. Einn býr á Íslandi, en hinir búa í Danmörku. (I have three brothers. One lives in Iceland, but the others live in Denmark.)

"Every Other"

To say "every other day" or "every other man," use Annar hver.

Annan hvern dag. (Every other day).
Annar hver maður. (Every other man).

"Each Other" (Hvor annar vs. Hver annar)

This is a classic Icelandic grammar trap. To say "They love each other," you have to ask: How many are "they"?.

Rule 1: The Number Rule

Hvor annar: Use this for exactly 2 people/groups.
Hver annar: Use this for more than 2 people/groups.

Rule 2: The Grammar Construction

The phrase is split into two parts.

Word 1 (Hvor/Hver): Matches the Subject (Nominative). These remain Singular even if the subject is plural!
Word 2 (Annar): Matches the Object (Case is decided by the verb or preposition).

Examples:

Bræðurnir tveir aðstoðuðu hvor annan. (The two brothers assisted each other.)
Vinkonurnar trúðu hvor annarri. (The two friends believed each other.)
Fólkið elskar hvert annað. (The people love each other.)

Rule 3: The Preposition Sandwich

If there is a preposition (við, hjá, með), it goes in the middle of the two words.

Þær horfðu hvor á aðra. (They looked at each other.)
Mennirnir rifust hver við annan. (The men argued with each other.)

The Shortcut (St-Sagnir / Middle Voice)

Sometimes, you can avoid the complex "hvor annar" construction entirely by using -st verbs (Middle Voice). Adding -st to the verb implies "to each other".

Jón og Anna heilsuðu hvort öðru = Jón og Anna heilsuðust.

How to Form St-Sagnir

You take the verb and add -st.

Group 1 (-ar): Heilsar → Heilsast (Present), Heilsaði → Heilsaðiust (Past).
Group 2 (-ir): Kyssir → Kyssist (Present), Kyssti → Kysstist (Past).
Group 3 (-ur) & Strong: Spyr → Spyrst (Present), Spurði → Spurðist (Past).

Common St-Verbs:

Hittast (To meet each other)
Heyrast (To hear each other / "Talk to you later")
Sjást (To see each other / "See you later")
Finnast (To be found / To exist)

Declining "Annar"

Since "Annar" is the second half of the phrase, you must know how to decline it. It has a few tricks, specifically the ö appearing in the feminine and neuter plural.