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Any shape wit four of more sides can have one pair of parallel sides.
A square
A polygon with 4 or more sides can have a pair of parallel sides.
A right hendecagon can have no parallel sides because there are eleven sides to a hendecagon. It is not a requirement that there be any pairs of parallel sides in an irregular hendecagon, although there could be one or more pairs.
Strictly speaking you cannot have one parallel side - you must have one pair. Any irregular polygon with four or more sides can have a pair of parallel sides. Most have no specific names - the only one that does is a trapezium.