AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
Dilution is the process of mixing an acid or base with water, which results in a decrease in the concentration of $\text{H}_3\text{O}^+$ or $\text{OH}^-$ ions per unit volume.
Source: Chapter 2, Section 2.2.1
The textbook's exact definition is key here: dilution = adding water → decrease in ion concentration per unit volume. Examiners expect both components — the action (mixing with water) and the effect (decrease in $\text{H}_3\text{O}^+$/$\text{OH}^-$ concentration). Don't confuse dilution with neutralisation.