Question

is a triangle a pollygon?

Answer 1

yes

Answer 2

what about a hexagon

Answer 3

Every enclosed shape by line segments is known as polygon

Answer 4

therefore hexagon is also a polygon :
There are two types of polygons : convex and concave ( just for your info.. )

Answer 5

Any figure enclosed by 3 or more straight lines is a polygon

A triangle has 3, and is enclosed. So, aye aye, it's a polygon alright, cap'n! ;)

Answer 6

Right @apoorvk as there is no enclosed figure having less than 3 line segments :)