Supine vs Past Participle

Here is a distinction that is invisible to English speakers and yet runs underneath two of the most important Icelandic constructions. English has one past form for both jobs — eaten, taken, written — and uses it after have (I have eaten) and in the passive (it was eaten) without changing a letter. Icelandic splits that one form into two: the supine, a single frozen shape that follows hafa in the perfect, and the past participle, a fully declined adjective that agrees with its subject in the passive and the vera-perfect. They often look the same in the neuter singular — which is exactly why learners overlook the split — but they behave completely differently, and choosing the wrong one breaks the sentence. This page is purely about telling the two apart and forming each correctly. (When to use the hafa- vs vera-perfect is covered on the perfect overview; the passive construction itself is on the passive overview.)

The supine: one frozen form after hafa

The supine is the verb form that follows the auxiliary hafa in the perfect tense. Its defining property is that it never changes — not for gender, not for number, not for case. Whoever the subject is, the supine sits there inert. It always ends in one of three ways:

• -að for weak -a verbs (the kalla/borða type): borðað, kallað, talað, elskað.
• -t for many other weak verbs: keypt (kaupa), lært (læra), sent (senda).
• -ið for strong verbs: tekið, gefið, lesið, komið, séð (the -ð sometimes appearing as -ið/-t/-ð on the strong stem).

Whatever the ending, the supine is a single dictionary form you memorise per verb — the fourth principal part of a strong verb, or the predictable -að/-t of a weak one.

Read that last one carefully: the subject strákarnir is masculine plural, yet the supine is still borðað — the bare neuter-looking shape. After hafa, the verb form does not care who the subject is. That is the whole personality of the supine.

The past participle: a declined adjective

The past participle is a different animal. It is built from the same stem but it behaves like a full adjective: it takes the strong adjective endings and agrees with whatever it describes in gender, number, and case. Its masculine/feminine/neuter base shapes are:

• weak verbs: -aður / -uð / -að (borðaður, borðuð, borðað),
• strong verbs: -inn / -in / -ið (tekinn, tekin, tekið).

You will recognise these endings — -aður and -inn are ordinary strong-adjective endings (the same family as þreyttur, þreytt, þreytt). The participle then declines through the whole adjective paradigm: plural borðaðir/borðaðar/borðuð, teknir/teknar/tekin, plus all the case forms. It is, grammatically, an adjective that happens to mean "having been V-ed."

This is the form you need in two places: the passive (bréfið var skrifað "the letter was written") and the vera-perfect of motion/change verbs (hún er farin "she has gone"). In both, it agrees with the subject.

Notice how the participle changes shape to match: neuter skrifað, feminine plural skrifaðar, masculine brotinn. That is exactly what the supine refused to do. The agreement is not optional decoration — it is how the participle works as an adjective.

The contrast in one table

The cleanest way to see the split is to lay the frozen supine beside the full participle paradigm — one weak verb (borða "eat") and one strong verb (taka "take"):

Two things jump out. First, the supine and the neuter singular participle are identical — borðað = borðað, tekið = tekið. This is the coincidence that hides the whole distinction from learners: in a sentence like þetta var borðað (neuter subject) the participle just happens to match the supine, so you never notice you switched systems. Second, the moment the subject is not neuter singular, the two diverge sharply: the supine stays borðað/tekið, but the participle becomes borðaður, borðaðar, tekinn, teknir… The split is real; the neuter singular merely camouflages it.

Why English speakers get this wrong

English fuses the two roles into one invariant word, so an English speaker has no instinct that there is a choice to make. The transfer error goes both directions. Coming from the perfect, learners over-apply agreement and try to make the form after hafa agree — \ég hef tekinn prófið — because they have learned that Icelandic participles agree, and they over-generalise. But after *hafa the form is the supine, frozen: ég hef tekið prófið. Coming from the passive, learners freeze the participle as a supine — *bækurnar voru skrifað — because in English written never changes. But in the passive the participle is an agreeing adjective: bækurnar voru skrifaðar. The single English form written has to be mentally split into a frozen skrifað (after hafa) and an agreeing skrifaður/skrifuð/skrifað/skrifaðir/skrifaðar (in the passive). Getting the split right is what makes both the perfect and the passive come out correct.

A note on case agreement

Because the participle is a true adjective, it agrees not only in gender and number but in case — which matters whenever it sits inside a phrase that isn't a plain nominative subject. After verbs that assign a non-nominative subject, or in predicate positions governed by case, the participle takes the matching case ending, exactly as an attributive adjective would. You will rarely build these consciously at B1, but it is worth knowing the supine never does this — another sign of how frozen it is.

That last example shows the endpoint of the participle's adjective nature: skrifuð there is doing exactly what góð "good" would do. The supine skrifað could never sit in that slot. (For the participle used purely as an adjective — soðið egg "a boiled egg," brotinn diskur "a broken plate" — see past participle as adjective.)

Common Mistakes

Key Takeaways

• Icelandic splits English's single -ed/-en into two forms: the supine (frozen) and the past participle (an agreeing adjective).
• The supine follows hafa in the perfect and never changes: -að (weak borða → borðað), -t (kaupa → keypt), -ið (strong taka → tekið).
• The past participle appears in the passive (var skrifað/skrifuð/skrifaðar) and the vera-perfect (er farinn/farin), and it agrees with its subject in gender, number, and case: -aður/-uð/-að (weak), -inn/-in/-ið (strong).
• They coincide only in the neuter singular (borðað = borðað), which is what hides the distinction from English speakers — but any non-neuter-singular subject pulls them apart.
• The fix is procedural: decide the slot first. After hafa → supine, no agreement. In the passive / vera-perfect → participle, agrees.