Site-level relevance
The publication regularly covers the broader market or discipline connected to your destination.
Page-level relevance
The individual article creates a natural context for the link. A broad publication can still produce a highly relevant page.
Destination relevance
The linked resource continues the reader's journey rather than interrupting it with an unrelated commercial page.
Avoid mechanical matching
Relevance is semantic, not just lexical. Closely related industries, tools, problems and audiences can create legitimate context even without identical keywords.