The iPad is arguably the best device for reading omnivores, and those users need to have a dictionary, whether it's for looking up full definitions of words from books or articles, or playing Scrabble. There are lots of great dictionary apps (and ebooks) that you can buy for the iPad, but they are surprisingly expensive (usually between $10-$30). The Dictionary.com app is well executed and it's free, although it has two ads that actively run on the page. You can also buy an ad-free version for $5.
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Credit: Jason Hiner | TechRepublic