A limb of a tree at a vertex 
is the union of one or more branches
at 
in the tree. 
is then called the base of the limb.
Limb
See also
Branch, TreeExplore with Wolfram|Alpha
References
Lu, T. "The Enumeration of Trees with and without Given Limbs." Disc. Math. 154, 153-165, 1996.Schwenk, A. "Almost All Trees are Cospectral." In New Directions in the Theory of Graphs (Ed. F. Harary). New York: Academic Press, pp. 275-307, 1973.Referenced on Wolfram|Alpha
LimbCite this as:
Weisstein, Eric W. "Limb." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Limb.html