Grounds and Solid ground

Grounds noun - Your basis for belief or disbelief; knowledge on which to base belief.

Solid ground is a synonym for grounds. In some cases you can use "Solid ground" instead a noun "Grounds".

Solid ground noun - The solid part of the earth's surface.

Grounds is a synonym for solid ground. Sometimes you can replace term "Grounds" with "Solid ground", this terms are similar.