Learn Dutch: Het zuiden is niet lager dan het noorden. - The south is not lower than the north.

When you add -er to make the comparative, the word gets an extra syllable: la-ger. Because the first syllable now ends in a vowel (an 'open' syllable), Dutch spelling rules say you only need one a to keep the long 'a' sound.

I sometimes hear Dutch people use als for comparisons. Why is it dan here?

When comparing two things that are unequal (one is lower, bigger, or faster than the other), the correct word for 'than' is dan. You only use als when things are exactly equal, like in even laag als (as low as).

Why does niet go right before lager?

The word niet usually goes right before the specific word or phrase it is negating. Because the sentence is specifically negating the idea that the south is 'lower than the north', niet sits directly in front of the comparative phrase.

Why aren't zuiden and noorden capitalized?

In Dutch, compass directions like zuiden (south) and noorden (north) are written in lowercase when they just refer to a direction or a general area. You only capitalize them if they are part of a specific, official name, like Zuid-Holland.