Number of results on Google Search:

"tuple elements" 21,500 results
"tuple fields"   10,100 results
"tuple members"   2,270 results

"record fields"   83,000 results
"record elements" 42,300 results
"record members"  30,500 results

"union members"  1,620,000 results
"union fields"      48,500 results
"union elements"    11,300 results