What does "growth" measure? If we buy a $7 kindle book rather than a $16 paper back does that halve GDP? We have improved medical care that costs the same doe

What does "growth" measure? If we buy a $7 kindle book rather than a $16 paper back does that halve GDP? We have improved medical care that costs the same does that imply no growth? If twice as many people use air travel, but it costs half as much does that mean there is no growth?