cachar - to understand, to see, to know
cachetear - to slap
calar - to soak, to cut a piece out to taste (frutas), to fret (madera), to make openwork (ropa)
calcar - to trace (dibujos)
calcificar - to calcify
calcinar - to calcine
caldear - to heat
calefaccionar - to heat (home heating system)
calibrar - to calibrate
calificar - to describe, to grade, to qualify
calzar - to shoe
cambiar - to change; to cash (a check)