Apologies if this question is inappropriate for the site.
In the US, what would be equivalent to the OED? The de facto standard. I know there's the New Oxford American Dictionary but in the US does this have the same gravitas as the OED has in the UK?
Probably the most famous American dictionary is the controversial Webster’s Third New International Dictionary, which made headlines when it was first published for taking a hard-line descriptivist stance, particularly for its treatment of the word ain’t. It remains the most important unabridged dictionary of American English, although it hasn’t received a major revision since it was first published in 1961.
The Merriam-Webster Collegiate Dictionary, which is shorter and can be held in one hand, remains Merriam-Webster’s flagship dictionary, receiving frequent updates and revisions. It is also the best-selling dictionary of American English. The online version is accessible at Merriam-Webster.com.
The other significant dictionary of American English is the American Heritage Dictionary, which was published by the owner of the history magazine American Heritage, who was appalled by the permissiveness of Webster’s Third. The American Heritage Dictionary is notable for pioneering the use of corpus linguistics in dictionary compilation, as well as for its 200-member “usage panel” who the dictionary consults when writing usage notes, reporting what percentage of the panel approved or disapproved of different contested usages.
There are othe American dictionaries which are well-regarded but not as well-known, such as the Oxford American, Random House, and Webster’s New World. Americans generally don’t distinguish among dictionaries and typically refer to all dictionaries as “the dictionary”, as in “I’ll look that up in the dictionary”.
The OED is a historical dictionary, which means it shows the meanings of words as they developed over time. People use it as a standard, but it does not set out to be one, and the editors of the OED discourage people from deciding whether or not to use a word based solely on its inclusion in the OED.
The New Oxford American Dictionary is not a historical dictionary, but a dictionary of current English, and is much smaller than the OED in the number of terms covered. (If you have a Mac, you already have this dictionary, because it's the dictionary used by the Dictionary Widget in the dashboard.)
If you are looking for a dictionary that set itself up as a standard, especially for scientific and technical vocabulary of the day you might look at the Century Dictionary(commentary at link). It has not been updated for about a hundred years, though.
The bigger question is: what do you want a standard for?
To tell you whether or not something is a word? No dictionary will tell you that, only usage.
Etymology? The OED is among the best for etymology, although there are other sites that have better ones for particular words (and despite the Century's age, its etymologies are on a par with the OED).
Advice on correct or accepted usage? You'd be better off with the Dictionary of Modern American Usage.
An impressive book to put on a stand? True dictionary aficionados like Merriam Webster's Second International (rather than the third), as a prestige thing. (Or again, a copy of the Century, although that's ten volumes.)
New Oxford American Dictionary (NOAD) is part of the great work done by the OED group and does pull the same weight as the rest of their publications. The major difference is that the NOAD presents the American variant spellings first and contains words and usage that are not used in other English dialects.
There isn't a standard, but the best sellers should have the greatest influence. Judging by the current best-sellers on Amazon, they are:
