Learn Icelandic: Ef hún gerði nýja tilraun, þyrfti hún einkaleyfið. - If she did a new experiment, she would need the patent.

For weak verbs like gera (verbs that form the normal past tense with -ði, -di, or -ti), the past subjunctive is completely identical to the normal past tense! We only know it is acting as the subjunctive here because the word ef (if) sets up an imaginary, hypothetical condition.

If weak verbs look identical in the past subjunctive, why is "would need" þyrfti instead of the normal past tense þurfti?

While standard weak verbs like gera don't change, some verbs undergo a vowel shift (called an i-shift) to form the past subjunctive. For the verb þurfa (to need), the u in the normal past tense þurfti (needed) shifts to a y, becoming the subjunctive þyrfti (would need).

Why does the second half of the sentence start with the verb, þyrfti hún (would need she)?

This is the V2 (verb-second) rule in action. The entire "if" clause (Ef hún gerði nýja tilraun) counts as the first block of information. To ensure the main verb stays in the second position of the sentence, þyrfti must come immediately after the comma, pushing the subject (hún) right after it.

Why is the adjective for "new" written as nýja here?