Khaki and Khakis

Khaki noun - A sturdy twilled cloth of a yellowish brown color used especially for military uniforms.

Khakis is a synonym for khaki. In some cases you can use "Khakis" instead a noun "Khaki".

Khakis noun - A military uniform made of khaki fabric.

Khaki is a synonym for khakis in light brown topic. You can use "Khaki" instead a noun "Khakis", if it concerns topics such as coordinated outfit, light brown color.