Q.What does an octave mean?
A.Eight notes in music.
_Non-agon_.
Q.What is this?
A.A nonagon.

Q.Why is it called a nonagon?
A.
Because it has nine sides and nine angles.

Q.What does a nonagon mean?
A.A nine-sided figure.

Q.What is an irregular nonagon?
A.A nine-sided figure whose sides and angles are not equal.
_Dec-agon_.
Q.What is this?
A.A regular decagon.

Q.What does a decagon mean?
A.
A ten-sided figure.