There is no such word as a dectagon. And since it could refer to an octagon or a decagon (or possibly something else), it is not possible to give a sensible answer. Please correct your spelling and resubmit the question.
Assuming that the question is meant to be about some polygon, it need not have any lines of symmetry.
A nephroid has 2 lines of symmetry.
It has 2 lines of symmetry.
no lines of symmetry
5 lines
A hectagon has 9 lines of symmetry!
A nephroid has 2 lines of symmetry.
it has five lines of symmetry
10 lines of symmetry
4 Lines of symmetry
2 lines OF SYMMETRY
2 lines of symmetry
It has 2 lines of symmetry.
no lines of symmetry
2 lines of symmetry
5 lines
There is no such thing as 8 lines of symmetry. A circle, for example, has infinitely many lines of symmetry.
There are infinitely many lines of symmetry. Every line can be a line of symmetry for a suitable shape.