Compression: A force that squeezes an object from opposite directions, pushing two points towards each other. Smashing a can with your foot puts it under compression.
Span: To extend from one side of something to the other side, as a bridge does over a river.
Tension: A force produced from stretching or pulling something in opposite directions. A tug-of-war rope is under tension.
Truss: A structure made out of triangle shapes and designed to carry heavy loads.