2 teaspoons white-wine vinegar
1/2 teaspoon sugar
1/4 teaspoon salt
2 tablespoons olive oil
1 seedless cucumber (1-1/4 pound; usually plastic-wrapped), cored and cut into 1/8-inch-thick matchsticks
1/2 pound jicama, peeled and cut into 1/8-inch-thick matchsticks (2 cups)
2 tablespoons drained bottled pickled ginger, finely chopped

Whisk together vinegar, sugar, and salt in a small bowl until sugar is dissolved, then add oil in a slow stream, whisking until emulsified. Toss together cucumber, jicama, ginger, and dressing in a bowl until combined well, then let stand, covered and chilled, 15 minutes.