这款产品的用户增长呈现S型曲线，初期缓慢，中期爆发，后期趋于稳定。

The user growth of this product followed an ___s-curve, starting slowly, then surging, and finally stabilizing.

这段山路有几个连续的S形弯道，驾驶时要格外小心。

There are several consecutive ___s-curves on this mountain road, so drive with extra caution.

在Lightroom中使用S曲线可以提升照片的明暗对比度。

Using an ___s-curve in Lightroom enhances the contrast between shadows and highlights.