6 BULLETIN 556, U. S. DEPARTMENT OF AGRICULTURE. 
MISUSE OF TERMS. 
Considerable confusion often arises from the use of general terms 
in a limited sense, or with different meanings by different persons. 
For instance, strength, in the broad sense of the word, is the summa- 
tion of the mechanical properties or the ability of a material to resist 
stresses or deformations of various sorts. While such properties as 
hardness, stiffness, and toughness are not always thought of in con- 
nection with the term "strength," they are unconsciously included 
when, in a specific instance, they are important. This may be 
illustrated by some comparisons of oak and longleaf pine. For 
floor beams or posts, the pine, because of its strength and stiffness as 
a beam, has a slight advantage over the oak and is considered 
"stronger." For handles, vehicle or implement parts, oak, because 
of its greater toughness, or shock-resisting ability, is decidedly 
superior to the pine and is considered "stronger." Thus it is seen 
that the term "strength" may refer to any one of many properties 
or combinations of properties, and is necessarily indefinite in meaning 
unless so modified as to indicate one particular thing. To say, then, 
that one species is stronger than another is a meaningless statement 
unless it is specified in what particular respect it excels. 
The term strength, in its more restricted sense, is the ability 
to resist stress of a single kind, or the stresses developed in one 
kind of a constructional member, as strength in shear, strength 
in compression, strength as a beam, strength as a column. Used in 
this way, the term is specific and allows no chance of confusion. 
RELATION OF PROPERTIES TO USES. 
There are many properties of wood, such as taste imparted to 
foodstuffs, odor, ease of working, ability to take finish and to main- 
tain shape, resistance to decay, etc., which, of course, are not given 
in the accompanying tables, but which are very important in some 
uses to which timber is put. In very few instances will strength 
data of themselves be sufficient to determine the value of a species 
for a given use. 
There are few, if any, cases in which two species have all the various 
properties to the same degree or in the same relative proportion. 
This fact accounts for the special uses of the different species and for 
the difficulty in finding substitutes for certain species in particular 
uses. Confusion arises from comparing species for a certain use upon 
the basis of properties or strength values which are not of first 
importance hi that use. The most important strength values are: In 
large beams, modulus of rupture, modulus of elasticity, and shear; in 
long columns, modulus of elasticity and crushing strength in com- 
pression parallel to grain; in material for spokes, tongues, or poles, 
ax handles, etc., modulus of rupture, modulus of elasticity, work to 
