Here's why:

* pH Scale: The pH scale measures how acidic or basic a substance is. It ranges from 0 to 14.

* Acidic: Substances with a pH below 7 are considered acidic.

* Basic (or Alkaline): Substances with a pH above 7 are considered basic.

* Neutral: A pH of 7 is neutral (like pure water).

So, lemon juice, with a pH below 7, is acidic.