What is deionized water? Can distilled water be called deionized water?

Hint: This is a conceptual question. It requires the understanding of water purification processes and the different forms of purified water. Distilled water is used for various chemical purposes and also for various industrial applications while deionized water is used mainly for chemical purposes only.

Complete answer:
Distilled water is water that has been boiled to remove toxins and impurities such as chlorine and dissolved solids, resulting in purified water. Although this might seem to be a brilliant idea, it is not the best option for drinking water.
While distilled water is safe to drink, the distillation process removes many of the naturally occurring and beneficial minerals from water, so using it as your regular drinking water can cause more harm than good in the long run.
Deionized water is a very pure source of water, similar to distilled water. Deionized water, on the other hand, is water that has had all of its ions extracted. This means it's usually used in conjunction with another form of treatment, such as reverse osmosis, to ensure that all pollutants are properly removed.
Since, like purified water, deionized water extracts virtually all minerals from the water, it is often referred to as "demineralized water." And, as with bottled water, though it is safe to drink, it may not be the best option for your drinking water needs because it eliminates beneficial minerals that many of us depend on from our tap water.

Note:
Deionized (DI) water is widely used in scientific applications where 100% pure water is needed for experiments, resulting in more predictable and repeatable results. For reasons of protection and quality, this form of water is often used in pharmaceutical applications.