A quality of design that takes possible future advances into consideration and attempts to accommodate them(noun)
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Use "extensibility" in a sentence
"Semantic extensibility is harder, but can also be done."
"Coflight is also the first FDP to enjoy an open architecture funded over Standard and Open Source middleware technologies to guarantee the long-term extensibility, scalability and availability of supply."
"We’ve built in extensibility points, so you can add functionality to Facebook Open Platform like your own tags and API methods."