2 certain or safe; of a good standard; giving confidence or support -- 確定的;紮實的;可信賴的
3 continuing for a period of time without stopping -- 持續的,不間斷的
4 an object that has a height, width, and length, and is not flat -- 立體;立體圖形
5 a substance that is not liquid or gas -- 固體物質
The construction should be sturdy and solid.
This theory needs to be backed up with solid empirical data.