This is the 1279th most frequent German word.
ernst
Serious.
In this sentence, 'ernst' (serious) is used as an adjective to describe the nature of the topic that requires thoughtful consideration.
Das ist ein ernstes Thema, das wir besprechen sollten.
This is a serious topic that we should discuss.
Here, 'ernst' functions as an adjective to describe the speaker’s demeanor and attitude towards the subject of the future.
Ich bin sehr ernst, wenn es um unsere Zukunft geht.
I am very serious when it comes to our future.
In this case, 'ernst' is used as an adverb to question the sincerity or gravity of the statement being made.