A dictionary is valid as a secondary source. Professors typically will not count these if they are looking for a specified number of sources, but they are good to backstop your primary (academic) sources.Click to see full answer. Besides, is a dictionary a credible source?It is important to note that encyclopedias or dictionaries, of any kind, including the very popular Wikipedia, Dictionary.com, and Merriam Webster Online, are not primary sources and should not be cited or used in constructing term papers at the undergraduate or graduate level. is the Merriam Webster Dictionary a reliable source? Merriam-Webster is a wonderful and reliable source for information. Then, is the Oxford Dictionary a reliable source? About. The Oxford English Dictionary (OED) is widely regarded as the accepted authority on the English language. It is an unsurpassed guide to the meaning, history, and pronunciation of 600,000 words— past and present—from across the English-speaking world. The OED started life more than 150 years ago.Which is the most reliable dictionary? Here are ten of the very best online dictionaries. Wiktionary. Google Dictionary. Dictionary.com. The Free Dictionary. Merriam-Webster Online. Cambridge Dictionary Online. Visuwords. Wordia.