Agent and Instrument Nouns

When Icelandic needs to name the one who does X — a teacher, a baker, an owner, a student — it has two main suffixes, and they sit in different corners of the grammar. The first is -ari, the close cousin of English -er: baka "bake" → bakari "baker", kenna "teach" → kennari "teacher". The second is -andi, built on the present participle: nema "study" → nemandi "student", eiga "own" → eigandi "owner". Both make masculine agent nouns, and at first glance they look interchangeable. They are not — and the place they part company is the plural. The -ari nouns are perfectly regular (kennari → kennarar); the -andi nouns have an irregular plural in -endur (nemandi → nemendur, never *nemandar). That one fact — same gender, two different plurals — is the heart of this page. Along the way, note that the -ari machinery does double duty for instrument nouns too: a thing that opens is an opnari "opener", a thing that dries is a þurrkari "dryer". (The -andi form's wider life — as an adverb in kom hlaupandi, as an attributive in rennandi vatn — is covered on word-formation/present-participle-andi; here we focus on the agent and instrument nouns and, above all, on getting the two plurals right.)

The -ari agent: bakari, kennari, leikari

The suffix -ari attaches to a verb stem and names the person (or thing) that performs the action — exactly like English -er in bake → baker. It is fully productive: hand it almost any verb and you get a usable doer.

These nouns are masculine and decline as ordinary weak masculines (the -i class): singular kennari / kennara / kennara / kennara, and the regular plural -arar: kennari → kennarar, bakari → bakarar, leikari → leikarar. Nothing surprising happens; once you know the weak-masculine pattern, every -ari noun follows it.

A point worth flagging: -ari attaches to the verb, so the doer of baka is bakari, not a noun-based form. And the noun is masculine even when it names a woman in its neutral, occupational sense — hún er kennari "she is a teacher", hún er leikari "she is an actor" — though a feminine pair sometimes exists (leikkona "actress"), now often avoided in favour of the gender-neutral leikari.

Instrument nouns: the same -ari for things, not just people

The -ari suffix does not only make people. Applied to a verb, it just as readily names the thing that does the action — an instrument. Opna "open" → opnari "(bottle/tin) opener"; þurrka "dry" → þurrkari "(clothes/tumble) dryer"; ryksuga "vacuum" → here the noun ryksuga "vacuum cleaner" is itself the tool (a slightly different formation), but blandari "blender" (from blanda "mix"), prentari "printer" (from prenta "print"), and vekjari "alarm (clock)" (from vekja "wake") all show the instrument -ari clearly. These are masculine and pluralise -arar, exactly like the human agents — so prentari → prentarar, opnari → opnarar.

So -ari is a single, very general "doer" suffix that covers both human agents and machines. The grammar is identical for both: masculine, weak-masculine declension, plural in -arar.

The -andi agent: nemandi, eigandi, stjórnandi

The second route to an agent noun is -andi, taken straight from the present participle. Nema "study" → nemandi "student", eiga "own" → eigandi "owner", stjórna "manage, direct" → stjórnandi "manager, conductor, director". Like the -ari nouns these are masculine, but they belong to a special declension class — and this is where the trap lives.

In the singular they end in -andi in the nominative and -anda elsewhere: nemandi / nemanda / nemanda / nemanda. But the plural is irregular, ending in -endur: nemandi → nemendur "students", eigandi → eigendur "owners", stjórnandi → stjórnendur "managers". This -andi → -endur shift is the one fact to lock in — and the one learners get wrong by regularising it to *nemandar.

The two classes side by side

Here is the contrast that the whole page turns on. Both suffixes make masculine agent nouns; the difference is entirely in the plural:

The reason for the irregular -endur plural is historical: the -andi nouns descend from the present participle of strong-style verbs, and -endur is a fossilised participial plural (cognate, distantly, with the -nd- in English friend, originally "the one loving", and fiend, "the one hating"). You don't need the history to use the words, but it explains why the plural looks nothing like the singular. Practically: when a doer-noun ends in -andi, reach for -endur in the plural; when it ends in -ari, reach for -arar.

Which suffix for which doer?

There is no fully predictive rule, and you should expect to learn each agent noun with its suffix — but two tendencies help. First, the everyday "occupation built straight from a verb" usually takes -ari: bakari, kennari, leikari, málari, prentari. Second, several high-frequency doers built on state or relation verbs — owning, studying, managing, standing for office — take -andi: eigandi, nemandi, stjórnandi, frambjóðandi. When both could exist, idiom decides: "teacher" is the -ari word kennari in daily use, even though the participial kennandi is formable. So: learn the lexical item, but if you must guess, a fresh verb-based occupation or tool tends to -ari.

English vs Icelandic

English funnels almost every agent and instrument through one suffix, -er: teacher, baker, owner, opener, dryer, printer — people and machines alike, with a single, regular plural -ers. Icelandic splits the job in two and, crucially, gives the two classes different plurals. The -ari class lines up neatly with English -er — same human-and-machine coverage, regular plural -arar — so it feels familiar. The -andi class is the one with no clean English parallel: it is built on the participle (so it looks like a verb form) and pluralises in -endur, which the English instinct toward "just add -s/-ar" will fight. The mental adjustment is to *tag each doer-noun with its suffix and its plural at the moment you learn it: kennari → kennarar (regular) versus nemandi → nemendur (irregular). Get that tag right and the rest of the declension follows the standard masculine patterns.

Common Mistakes

The signature error: regularising the irregular plural. Nemandi → nemendur, eigandi → eigendur, stjórnandi → stjórnendur.

The mirror error: applying the -endur plural to an -ari noun. -ari always takes the regular -arar.

Agent nouns build on the verb stem: baka → bakari. Don't import an umlaut or a noun base.

Instrument -ari nouns follow the regular -arar plural just like human -ari agents — never the -endur of the -andi class.

Eigandi belongs to the -andi class; its plural is eigendur, like nemendur and stjórnendur.

Key Takeaways

• Icelandic makes agent nouns two ways: -ari (from a verb stem: bakari, kennari, leikari) and -andi (from the present participle: nemandi, eigandi, stjórnandi). Both are masculine.
• The classes split on the plural: -ari → -arar (regular: kennari → kennarar) versus -andi → -endur (irregular: nemandi → nemendur).
• Instrument nouns use the -ari machinery (opnari "opener", þurrkari "dryer", prentari "printer") and pluralise -arar like human agents.
• The -andi singular runs nemandi / nemanda; only the plural is the surprise (nemendur, eigendur, stjórnendur).
• No fully predictive rule for which suffix — learn each doer with its suffix and plural — but fresh verb-based occupations and tools tend to -ari. </content>