A regular one has internal angles of 140 degrees

• Shape whose interior angles total 1,260 degrees
• Drama introduces Harry: touching figure!
• It has nine angles and nine sides
• Many-sided figure
• A nine-sided polygon
• Figure a small number continue to badger
• News about Bosnia regularly ignored – go figure
• Figure of horse appearing in middle of day

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
"plane figure with nine sides," 1680s, a hybrid from Latin nonus "ninth" (see nones ) + ending from pentagon , etc.