A dictionary is beneficial because it can help a person learn more about a particular word such as what the meaning of the word is, if the word should be capitalized, what the syllables of the word are, how to pronounce the word, the history of the word and can also help non-native speakers understand foreign words or phrases. Dictionaries also offer a sentence or an expression that uses the word so that the reader can get a better sense of how the word might be viewed in context.
Dictionaries are also able to link other similar words (synonyms). While some words cannot be interchanged, more words will expand one’s vocabulary. This is useful especially when one is reading academic books or some saturated article.
Thanks to the Internet, online dictionaries also prove to be useful.