Learn Danish: Vi er i gang med at bygge en dæmning på fem kilometer. - We are in the process of building a five-kilometer dam.

In Danish, the preposition på is commonly used to express the physical dimensions, age, or size of a noun. While English usually forms a compound adjective like 'a five-kilometer dam', Danish uses på plus the measurement, functioning similarly to saying 'a dam of five kilometers'.

What is the difference between saying Vi bygger and Vi er i gang med at bygge?

Danish doesn't have an exact structural equivalent to the English continuous tense (the '-ing' form). While Vi bygger can mean both 'We build' and 'We are building', using the specific construction at være i gang med at followed by an infinitive strongly emphasizes that you are actively in the middle of the process at this very moment.

Could I write femkilometer as one combined word here?

No, numbers and their units of measurement are kept as separate words in this context. You must write fem kilometer. You might see them combined if they form the first part of a larger compound noun (like 'et femkilometerløb'), but as a standalone measurement after the preposition på, they always remain separate.

How does the noun dæmning (dam) relate to its root verb?

Dæmning is derived from the verb at dæmme, which means 'to dam' or 'to stem'. The suffix -ning is a very common way in Danish to turn a verb into a noun, similar to how English uses '-ing' or '-tion' to create action-based nouns.