What do I mean by "fast"

When talking about languages

• At the hardware level -> Optimizations
• Assembly -> Instructions
• LLVM / Virtual Machine -> Intermediate Representation/Target
• Logic -> How easy is it to write something performant
• Standard Library -> Do we have to rewrite parts?
• Ideas -> Pivoting to new ideas
• How well can we measure performance? -> Control and Iteration
• Ecosystem -> Do people care?