Question

Why might some words in a text be in bold-faced type?

1.They might be definitions or key concepts.

2.They might contain information from an outside source.

3.They might be historical information.

4.They might be proper nouns.

Answer 1

I think “1, they might be definitions or key concepts” makes sense.
Hope this helps

Answer 2

The answer is 1. They might be definitions or key concepts