el silbato - whistle
  el semestre - six-month period, half a year, semester
  la sidra - cider (usually alcoholic)
  el retazo - remnant, fragment, small piece, snippet
  el reposacabezas - headrest
  el rabino, la rabina - rabbi
  el rédito - interest (as on an account), yield...
  redomado - out-and-out, outright, to the...
  la rama - branch (most meanings, including the...
  el rizo - curl, ripple, loop
  rocambolesco - far-fetched, incredible, hard to...
  el reloj - clock, watch, timepiece
  rojizo - reddish
  el refresco - soft drink, liquid refreshment, soda...
  el refugio - refuge, shelter
  el regazo - lap
  la rutina - routine
  rudo - rough (said of things or people),...
  rotundo - emphatic, definitive, categorical,...
  la rosquilla - ring-shaped pastry, doughnut