In Icelandic, the numbers 1, 2, 3, and 4 change their forms based on grammatical case. In this lesson, we will focus entirely on the genitive forms. You will use these forms to express measurements, duration, possession, and after certain prepositions (like vegna, meaning "because of").
| Number | Genitive Form |
|---|
| 1 (plural) | einna |
| 2 | tveggja |
| 3 | þriggja |
| 4 | fjögurra |
Notice that the number one (einn) has a plural genitive form: einna. While "one" is usually singular, this plural form is required when counting plural-only nouns, such as mistök (mistakes).
Duration and Measurements
A very common use for genitive numbers is combining them with a unit of measurement to describe a noun. In English, we say "a two-hour sleep" or "a three-meter stick". In Icelandic, you express this by putting both the number and the unit of measurement in the genitive case.
For example, to say "two-hour", you use tveggja (two) + tíma (hours). To say "three-minute", you use þriggja (three) + mínútna (minutes).
Dimensions, Groups, and Verbs
You will also use these genitive numbers when expressing exact dimensions (like length and width), when referring to a specific group of people, or when a verb explicitly requires its object to be in the genitive case (such as krefjast, meaning "to require").