“18, 5 Valencia: Commercial Philippine Timbers 511 
Shear.—Shear is the name of the stress which tends to keep 
fwo adjoining planes or surfaces of a body from sliding, 
one ‘on the other, under the influence of two equal and parallel 
forces acting in opposite directions. A force which produces 
shear in a material is called a shearing force. 
Strain.—The deformation or distortion produced by a stress 
or force is known as strain. 
Stress.—Stress is the force or set of forces applied to a body, 
and which tend to produce a strain. Fiber stress is the distrib- 
uted force tending to compress, tear apart, or change the 
relative position of the wood fibers. 
