Deionized Water vs. Demineralized Water

Step 1: Google relative terms: http://www.google.com/search?hl=en&q=demineralized+water+deionized&btnG=Search

Step 2: Find good match to what you are looking for: http://en.wikipedia.org/wiki/Distilled_water

Step 3: Find relative terms: "Deionized water which is also known as demineralized water ... is water that has had its mineral ions removed, such as cations from sodium, calcium, iron, copper and anions such as chloride and bromide."

Simple as that. It seems as though they can be used interchangeably.