The linked article states that CSS breakpoints should group "similar" screen sizes and thus be at:

• 600px "narrow"
• 900px "medium"
• 1200px "wide"
• (1800px) "huge"

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By choosing these breakpoints, most device screens will be somewhere between two breakpoints, and not at the very edge of them.

The ranges could be called:

• narrow (< narrow)
• medium (narrow - medium)
• normal (medium - wide)
• wide (wide - huge)
• huge (> huge)