A more thorough explanation:

Definition: To prove that something is true or exists, usually with evidence.

Example 1: The scientist was able to substantiate her theory with data from her experiments.

Example 2: The lawyer needed to substantiate her client's alibi with witnesses and other evidence.

These examples illustrate how substantiate means to provide evidence or proof to support a claim or statement. In the first example, the scientist was able to prove her theory by using data from her experiments. In the second example, the lawyer needed to provide evidence to support her client's alibi in order to prove their innocence.