x-axis maybe?
are you asking for help on finding definition for geometric terms? if so go to: http://library.thinkquest.org/2647/geometry/glossary.htm#b and to wikipedia for x and j terms
altitude
X bar. X axis.
There are no geometry terms that start with the letter J. Geometry deals with the spatial relationships of objects.
Skew
formula
I know one is X-Axis
x axsis
hexagon hypotenuse
X-axis and x-intercept start with x.
circle cylinder circumference cone
Trapezoid and triangle are geometry terms. They begin with T.