Questions & Answers about Das Glück ist wichtig.
Because Glück is a noun, and all nouns are capitalized in German.
So in this sentence:
- Das = article
- Glück = noun
- ist = verb
- wichtig = adjective
This is one of the first big spelling differences English speakers notice in German.
Because Glück is a neuter noun, so its article is das.
In German, every noun has a grammatical gender:
- der = masculine
- die = feminine
- das = neuter
So you learn the noun together with its article:
- das Glück
The article here is also in the nominative singular, because das Glück is the subject of the sentence.