Questions & Answers about Hjörtu og lungu eru mikilvæg líffæri.
Why do hjarta and lunga end in -u here instead of standard plural endings?
They belong to a tiny, closed group of weak neuter nouns, which only includes auga, eyra, hjarta, and lunga. For these four words, the nominative and accusative plural forms always end in -u, giving us hjörtu and lungu.
Why does the root vowel change from 'a' in hjarta to 'ö' in hjörtu?
This is caused by U-mutation. The -u plural ending triggers the root vowel a to shift to ö. You will also see this happen in the dative plural form, hjörtum. Since lunga already has a u in the root, it does not undergo this change.
Why does the adjective take the form mikilvæg?
Mikilvæg is the strong nominative plural neuter form of the adjective mikilvægur. It agrees with the neuter plural noun líffæri. If the sentence were singular, it would use the singular neuter form: hjartað er mikilvægt líffæri (the heart is an important organ).
How do we know líffæri is plural here when it looks identical to the singular form?