Simple Definition:

Alkaline is a term used to describe substances that have a high pH level, meaning they are basic or opposite of acidic. These substances can neutralize acids and often taste bitter. Examples of alkaline substances include baking soda (a type of salt) and milk of magnesia (a liquid medicine used for digestion).

Very Simple Definition:

Alkaline is a word used to talk about things that are the opposite of acidic. It means something is not sour but can taste bitter. Some examples are baking soda and bleach.