Discussing the Past: "What if?"
To discuss situations that didn't happen and their hypothetical outcomes, Icelandic uses the past perfect subjunctive. This combines the past subjunctive of the helper verb hafa (to have) with the supine of the main verb.
Here is how to conjugate the past subjunctive of hafa:
| Pronoun | Form | Pronoun | Form |
|---|---|---|---|
| ég | hefði | við | hefðum |
| þú | hefðir | þið | hefðuð |
| hann / hún / það | hefði | þeir / þær / þau | hefðu |
The "If" Clause
To say "If [someone] had [done something]", use ef (if) + subject + the correct form of hefði + the supine.
The Main Clause
For the consequence (the "...would have [done something]" part), you can simply repeat the hefði + supine structure.
If the ef clause comes first, it occupies the first position in the sentence. Due to the V2 (verb-second) rule, the main clause must begin with its verb (hefði), followed by the subject.
| If they had ignored the danger sign, the outcome would have been miserable. | Ef þeir hefðu hunsað hættumerkið, hefði útkoman orðið ömurleg. |
| If we had foreseen the collapse, we would have averted it. | Ef við hefðum séð hrunið fyrir, hefðum við afstýrt því. |
An Alternative: "myndi hafa"
You can also form the main clause using myndi (would) + hafa + the supine. The V2 rule still applies: if the main clause comes second, myndi precedes the subject.
| If one had seen the danger sign, one would have averted the collapse. | Ef maður hefði séð hættumerkið, myndi maður hafa afstýrt hruninu. |
Changing the Order
You can state the consequence first and the condition second. The sentence starts with a standard main clause (subject first). The "if" clause still uses ef + hefði + supine.
| The outcome would have been miserable if the police had not arrived in time. | Útkoman myndi hafa orðið ömurleg ef lögreglan hefði ekki komið tímanlega. |
| I would have listened to the advice if I had seen the danger sign. | Ég hefði hlustað á ráðlegginguna ef ég hefði séð hættumerkið. |