Create rotateY entry for CSS

content/css/concepts/transform-functions/terms/rotateY/rotateY.md

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+---
+Title: 'rotateY()'
+Description: 'Rotates an element around the Y-axis in 3D space.'
+Subjects:
+  - 'Web Development'
+  - 'Web Design'
+Tags:
+  - 'CSS'
+  - '3D Transforms'
+  - 'Animations'
+CatalogContent:
+  - 'learn-css'
+  - '3d-transforms'
+  - 'css-transforms'
+  - 'transform-functions'
+---
+
+The `rotateY()` function is a CSS transform function that allows you to rotate an element around the Y-axis (the vertical axis) in 3D space. This function is particularly useful for creating 3D effects and animations on web pages.
+
+## Syntax
+
+```css
+transform: rotateY(angle);
+```
+
+**Parameters:**
+
+- `angle`: The angle of rotation, which can be specified in degrees (deg) or radians (rad). Positive values rotate the element clockwise, while negative values rotate it counterclockwise.
+
+## Example
+
+```css
+.box {
+  transform: rotateY(45deg);}
+```
+
+In this example, the element with the class `box` will be rotated 45 degrees around the Y-axis.
+
+> **Note:**
+
+The `rotateY` function is supported in all modern browsers, but it's always a good idea to check for compatibility if you're targeting older browsers.
+