1 This implies that the other two sides are of equal length, and that the diagonals are of equal length. 2  An alternative definition is: a quadrilateral with an axis of symmetry bisecting one pair of opposite sides. 3  Trapezium (NAm.): no sides are parallel.
An enumeration date commonly refers to the official or control date set for a particular enumeration event such as a census. The official enumeration date may vary from one enumeration to the next. The enumeration date is a control function for collecting data over a broad space of time. All data collected is based on its validity as of a single date, no matter what date the information is taken within the enumeration period.
The enumeration date is as you surmised the actual date the info was recorded. The official enumeration date was 1 June 1850, all questions were to refer to that date. So she probably died sometime between 1 June and Sept 11. Don.