To determine how many squares can be formed with two or more vertices from the set {A, B, C, D}, we start by analyzing squares with varying numbers of vertices selected from this set.
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Counting Squares with 2 Vertices: Selecting 2 vertices from the square will not form a square, as two points only define a line segment, not a square. Thus, there are no squares with exactly 2 vertices.
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Counting Squares with 3 Vertices: Similar to the situation with 2 vertices, 3 points selected from a square cannot form a square, as three points define a triangle or a corner of a square, but not a complete square. Thus, there are no squares with exactly 3 vertices.
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Counting Squares with 4 Vertices: The only square that can be formed using all 4 vertices A, B, C, and D is the square ABCD itself. Therefore, we have:
\[ \text{Number of squares with 4 vertices} = 1 \]
In conclusion, the possible squares that can be formed with two or more vertices from the set {A, B, C, D} are as follows:
- 2 vertices: 0 squares
- 3 vertices: 0 squares
- 4 vertices: 1 square (ABCD)
Adding these together, the total number of unique squares that can be formed with two or more vertices in the set is:
\[ \text{Total} = 0 + 0 + 1 = 1 \]
Thus, the final answer is:
\[ \boxed{1} \]