Learn Swedish: Idag har vi en kort lektion. - Today we have a short lesson.

Swedish uses the V2 rule, which means the verb must be the second piece of information in a main sentence. Since this sentence starts with the time word Idag, the verb har must come immediately next, pushing the subject vi to the third spot.

Why does the adjective kort stay in its base form without any added endings?

Because it describes lektion, which is an en-word. We know it is an en-word because of the article en right before it. When an adjective describes a single en-word, it stays in its base form. If it were describing an ett-word, it would get a -t at the end.

Is it also correct to write Idag as two separate words?

Yes! You will often see both idag and i dag written by native speakers. They are both completely correct and mean exactly the same thing.

Does the ending of lektion sound like the English word action?

No, the -tion ending in Swedish is pronounced very differently. It makes a special sound similar to a soft 'sh' or a hollow 'hw', just like the first sound in the Swedish word sju (seven).