xylophone
Xenon is a chemical element. It begins with the letter x.
A river strating with X in Brazil is Xingu.xingu
Xianjindao is a volcano in North Korea. It begins with the letter x.
Xebec, xenia, xeric, xi, xylene and xylose are words. They begin with the letter x.
mk
bisector
X-axis and x-intercept start with x.
I think vertex...
Angle Apothem AxesAxiom
nonagon
width
A word that starts with X is a xylophone.
in geometry, width
centagan: 100-gon
The word you are looking for is:Trigonometry
How about a decagon which is a ten sided polygon