Q. In Merriam-Webster's Collegiate Dictionary the word mentalist, defined as "mind reader," is given a date of first use of 1925. What is the source for this date?

A. As of the 2008 printing of Merriam-Webster's Collegiate Dictionary, Eleventh Edition, the date of the first known use of the word mentalist has been pushed back to 1909. The citation for this date comes from the Syracuse Herald Journal of June 6 of that year, in a bulletin that reads: "Special Engagement of Pearl Tangeley The Egyptian Mentalist. The most astounding exhibition of mental telepathy ever witnessed."

The 1925 date from your original query was taken from the July issue of The Sphinx: "Attention Mentalists!" "Dating" dictionary entries is an ongoing process, and as new resources become available (such as searchable indexes and databases) we are frequently able to find earlier citations.

Q. Your definition for Plains is written as: "of or relating to North American Indians of the Great Plains or to their culture." Under 'function' it says it is an adjective, but isn't it a noun when used in this manner?

A. Plains as we define it is an adjective, though it is one that lacks many of the characteristics that often distinguish an adjective from other classes of words.

Plains generally appears in such phrases as Plains culture, Plains people, or Plains artifacts. In these phrases, Plains takes on the prepositive attributive function of an adjective and modifies the nouns which follow it. The adjective Plains does not, however, exhibit other behaviors often associated with adjectives: it is not gradable (one would not say "more Plains" or "most Plains"), it cannot be modified by "very," and it cannot be used after the verb ("this artifact is Plains").

It's true that Plains behaves more like an attributive noun (a noun which is used to modify another noun such as apple in the phrase apple pie) — but there is no noun use of Plains that corresponds with this attributive use. That is, there is no noun Plains that functions as a synonym for "North American Indians of the Great Plains." Plains is used as a synonym for Great Plains, but the adjectival usage that we define specifically refers not just to the Plains themselves, but to the people and culture of the Great Plains.

Q. I cannot find tricentennial in the dictionary. Is this an oversight, did I misspell it, or does the word simply not exist in the English language?

A. Tricentennial is a word. Originally the words most commonly used for a 300th anniversary or its celebration were tercentenary and tercentennial. Webster's New International Dictionary, Second Edition (1934) did include an entry for tricentennial, but no entry for tricentennial was included in the Third Edition (1961). The Oxford English Dictionary does include an entry for tricentennial, but it considers the word to be rare. We have been tracking contemporary use of tricentennial and the evidence clearly suggests that tricentennial is now far more common than tercentennial and tercentenary combined. It can be found in some other reputable desk-sized dictionaries and it is widely used in professionally written and edited English. Based on this evidence, we would suspect that tricentennial would be a high-priority candidate for inclusion in future revisions to our dictionaries (see www.merriam-webster.com/help/faq/words_in.htm for an explanation of this process).