Compound Spelling and Hyphenation

Icelandic builds vocabulary by stacking words together, and the first thing an English speaker must unlearn is the space. Where English writes television schedule as two words, high school as two words, bus stop as two words, Icelandic writes the equivalent compound as one unbroken word: sjónvarpsdagskrá, menntaskóli, strætóstoppistöð. This is not a stylistic preference — a space inside a compound is a spelling error in Icelandic, the same kind of error as a missing accent. This page is about how compounds are written — solid, with a genitive link, and with a hyphen only in three narrow situations. (How compounds inflect and take their gender from the final element is a matter of noun grammar, covered separately.)

The core rule: compounds are written solid

A compound in Icelandic is one word, written with no space and no hyphen, no matter how long it gets. The components simply run together, and the whole thing inflects on its last element. Length is no excuse to break it up: sjónvarpsdagskrá ("TV schedule," from sjónvarp + dagskrá) is one word; so is a four-part monster like Vetrarólympíuleikarnir ("the Winter Olympic Games").

The genitive link inside compounds

Many compounds glue their parts together with a genitive linking element — usually an -s- or -ar- — sitting between the first and second part. This is not a separate word; it is welded inside the single solid form. In sjónvarpsdagskrá, the -s- is the genitive of sjónvarp; in barnabók ("children's book"), the -a- links barn to bók; in sólar**hringur ("a 24-hour period," literally "sun-circle"), the -ar- links sól to hringur. The link is part of the spelling of the word — you write it without a break.

Whether a given compound takes -s-, -ar-, -a-, or no link at all is governed by the first element's noun class, and is best learned word by word with the noun pages. For spelling, the point is only this: the link, whatever it is, lives inside the single written word.

When a hyphen DOES appear

Icelandic uses the hyphen sparingly, for three specific jobs. Outside these, a hyphen between two ordinary words is wrong — that is the English habit, not the Icelandic one.

1. Coordinated ("suspended") compounds

This is the most distinctive use, and the one with no clean English parallel. When two compounds share their final element, Icelandic can write the shared element once, at the end, and replace it in the first compound with a hyphen. So "import and export" — innflutningur and útflutningur, both ending in -flutningur — is written inn- og útflutningur, with the hyphen standing in for the elided -flutningur. The hyphen marks a "hanging" stem that is waiting for the shared element to arrive at the end of the phrase.

This is genuinely a different device from anything in English. English, having no solid compounds to begin with, simply repeats the head word or relies on the noun standing alone: "water and air pollution," "import and export" (where -port happens to be shared but is never elided this way). Icelandic, because its compounds are solid, needs a way to avoid writing the long shared tail twice — and the suspended hyphen is that tool. Read it as "the first stem plus the final element that shows up after the coordinator."

2. Acronyms and abbreviations before an inflectional ending

When a compound is built on an acronym, initialism, or number and then needs a native ending or a second element, a hyphen separates the unchangeable abbreviation from the Icelandic material. So ESB (the EU) plus ríki ("state") is written ESB-ríki ("EU state"); a PCR-test is PCR-próf; a 5G network is 5G-net. The hyphen keeps the all-caps or numeric block visually intact while still letting the word inflect on the part after it.

When you decline such a form, the ending attaches after a hyphen too: ESB in the dative plural can appear as ESB-ríkjunum, and a possessive of a lone acronym is written like RÚV-s (genitive of RÚV, the broadcaster). The hyphen is the seam between the foreign/abbreviated block and the native inflection.

3. To avoid a triple letter or genuine ambiguity

Occasionally joining two parts would stack three identical letters at the seam — when the first element ends in the same letter the second begins with. The official spelling rules allow (but do not require) a hyphen there for legibility. The standard textbook case is gler ("glass") + rúða ("pane"): fused, it would be glerrúða with a double r across the seam, and if a third r threatened to pile up, a hyphen could break it. The rule also permits a hyphen where the fused form would accidentally spell a different, misleading word. This is an optional clarity device, not a frequent one — most compounds simply keep their doubled letters and stay solid.

How this differs from English

English noun compounds are usually open (two or more separate words: bus stop, high school, weather forecast) and only sometimes hyphenated or closed. Icelandic is the mirror image: its default is closed/solid, and the open spelling is simply wrong. So an English speaker's instinct — leave a space, or reach for a hyphen — produces errors in both directions. You must (a) close the space that English would leave, and (b) resist the hyphen that English might insert, reserving it for the three jobs above. The one device English lacks entirely is the suspended compound (inn- og útflutningur); English handles the same idea by writing the shared word out in full, so when you read a stem-plus-hyphen-plus-og, supply the missing ending mentally.

Common Mistakes

The space is the classic English-transfer error. Icelandic compounds are always one word, however long.

Over-hyphenating is the other transfer error. A hyphen between two normal Icelandic words is wrong; reserve it for suspended compounds, acronyms, and triple-letter clarity.

Writing the shared tail twice is grammatical but reads as un-idiomatic. Native style suspends it with a hyphen.

An all-caps initialism takes a hyphen before the native element it combines with, so the block stays visually intact.

Key Takeaways

• Compounds are written SOLID — one unbroken word, however long (sjónvarpsdagskrá, menntaskóli). A space inside a compound is a spelling error.
• A genitive link (-s-, -ar-, -a-) often welds the parts together inside the single word (veðurspá, barnabók).
• The hyphen has only three jobs: (1) suspended/coordinated compounds sharing a final element (inn- og útflutningur, vatns- og loftmengun); (2) acronyms/numbers plus native material (ESB-ríki, PCR-próf, 5G-net); (3) breaking a triple letter or genuine ambiguity for legibility.
• The suspended hyphen points rightward to a shared ending — read vatns- og loftmengun as vatnsmengun og loftmengun. English has no equivalent and just repeats the whole word.
• English defaults to open/hyphenated compounds; Icelandic defaults to solid. Close the space, resist the stray hyphen.