Emerging technologies are those technical innovations that represent progressive innovations within a field for competitive advantage. wikipedia 
The criteria for this list is that the technology must:
1. Exist in some way; purely hypothetical technologies cannot be considered emerging and should be covered at list of hypothetical technologies instead. However, technologies being actively researched and prototyped are acceptable.
1. Have a Wikipedia article covering them.
1. Not be widely used yet. Mainstream or commercialized technologies cannot be considered emerging.
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International Congress Innovation and Technology XXI: Strategies and Policies Towards the XXI Century, & Soares, O. D. D. (1997). Innovation and technology: Strategies and policies. Dordrecht: Kluwer Academic.