Learn Swedish: Månen bleknade bakom molnet. - The moon faded behind the cloud.

It is built from the adjective blek, which means pale. By adding the suffix -na, we get the verb blekna (to become pale, or to fade). This is the classic way to create inchoative verbs, which describe a change of state. Here it takes the past tense ending to become bleknade.

Is blekna always a Group 1 verb?

Yes! Almost all of these change-of-state verbs ending in -na belong to Group 1. This means they are very predictable to conjugate: you just add -r for present tense (bleknar) and -de for past tense (bleknade).

Does bleknade mean the moon was bleaching the cloud?

No, verbs created with this -na ending only describe what happens to the subject itself, without an object receiving the action. The moon isn't doing something to the cloud; the moon itself is becoming pale. If you wanted to say someone bleached something, you would use the related verb bleka.

Why do we say månen and molnet with different endings when they both mean 'the'?