A pair of opposite sides of a trapezium are ______.
parallel
Step 1: A trapezium is a 4-sided shape (a quadrilateral).
Step 2: By definition, it has one pair of opposite sides that are parallel.
Step 3: “Parallel” means two lines never meet, even if extended. We write it as \(\parallel\).
Step 4: For example, in a trapezium \(ABCD\), one pair—say \(AB\) and \(CD\)—are parallel:
\(AB \parallel CD\)
Step 5: The other pair \(BC\) and \(AD\) are not parallel.
Conclusion: The blank is parallel.