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)