| The two pairs of adjacent sides are equal. | |
| | The two pairs of opposite sides are parallel. | |
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| The two pairs of opposite sides are parallel, and all angles are right angles. | |
| | The two pairs of opposite sides are parallel, and all four sides are equal. | |
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| The two pairs of opposite sides are parallel, all sides are congruent, and all angles are right angles. | |
| | Only one pair of opposite sides must be parallel. | |
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