Learn Polish: Dobranoc! Idę spać. - Good night! I am going to sleep.

The word dobranoc is a combination of dobra (good) and noc (night). We use the feminine form dobra because noc is a feminine noun, even though it ends in a consonant instead of the typical feminine "-a".

Where is the word for "I" in the sentence "Idę spać"?

In Polish, the verb ending tells you who is doing the action. The -ę ending in idę already means "I am going". Adding the word ja (I) is not necessary and would actually sound unnatural here.

Does idę just mean "to go" in general?

Not quite! Idę specifically means "I am going on foot" right now. If you were taking a car or bus, you would use a different verb (jadę). Since you generally walk to your bed, idę is exactly what you need here!

Why does spać stay in its dictionary form?

When you use two verbs together to say you are going to do an action, only the first verb changes to match the person. Since idę is already changed to match "I", the second verb spać stays in its basic infinitive form (meaning "to sleep").