I've always understood the adjective -odd used in combination to mean about, as in "She read 300-odd pages and then stopped." After reading a comment by Edwin Ashworth in another question ("And doesn't even OED only define 600 000-odd words?") I looked up definitions of -odd and was surprised to find that they differ:
I. More than the number indicated
Somewhat more than the indicated approximate quantity, extent, or degree —usually used in combination 300-odd pages m-w
(In combination) Used to designate an indefinite quantity more than the quantity specified in round numbers: fifty-odd pounds. Collins (print)
With a relatively small number over that specified (usually in hyphenated compounds) twenty-odd children. Webster's New World Dictionary
Additional to a whole mentioned in round numbers, or to any other specified whole: following and when it takes the place of a unit appended to a ten.
A fortnight and odd days. Shak., R and J, i.3.15.
Eighty-odd years of sorrow have I seen. Shak. Rich. III. iv.1.96. The Century Dictionary
Edwin pointed out the curious take on this in the AHD:
Being in excess of the indicated or approximate number, extent, or degree. Often used in combination: invited 30-odd guests.
Webster's II New College Dictionary, also published by Houghton Mifflin, has an almost identical definition.
(Would you really use odd with a number that was not an approximation, e.g., "There were 123-odd books fitting the description"?)
The expression + odd refers to a relatively small amount over that specified; e.g. 300 odd means 'slightly over 300' D. Biber, S. Johansson, and G. Leech; Grammar of Spoken and Written English
And, for good measure, a textbook published by Routlege:
Let's look at some more sentences and see how the hyphen changes the meaning of the sentence.
- (Thirty odd) students tried out for the play.
We can say "thirty odd" students, which denotes that those thirty students are peculiar.
Or we can say "thirty-odd" students, which means 30+ students. D. Crovitz and M. Devereaux; More Grammar to Get Things Done (2020)
Informal: a little more than a particular number — used in combination with a number
The book's only 100-odd pages long. [=only slightly more than 100 pages long] The Britannica Dictionary
II. Approximately the number indicated
Immediately following the numeral (usually one that denotes multiples of ten) forming a phrase preceding the noun modified. Now often in weakened use (frequently hyphenated): ‘or so’; ‘or thereabouts’ (OED)
Examining the OED's citations for this sense (1597–1995), I find it impossible to tell which of the more recent ones fall under the parent definition
More generally: used to denote a remainder or numerical surplus over and above a ‘round number’ (as a multiple of ten or a similar unit such as dozen, etc.)
and which were intended by the author as "about."
You use odd after a number to indicate that it is only approximate.
How many pages was it, 500 odd?
He has now appeared in sixty odd films. Collins online
(I would always keep the hyphen; we've all seen some very odd films.)
Used after a number, especially a number that can be divided by ten, to show that the exact number is not known:
I'd say Robert's about 40-odd - maybe 45. Cambridge
The most common ways of giving an approximate number are as follows:
[informal] She's got twenty-odd cats.
Cambridge International Dictionary of English, p.58 (1995)
Note the following informal ways of indicating approximate numbers:
some eight people [some unstressed]
80-odd people [but not *85-odd people]
80 people or so/thereabouts
80 or so people
a good eighty people ['at least 80']
(R. Quirk et al.; A Comprehensive Grammar of the English Language, p. 395)
These five alternatives are bracketed with ['about eight'] alongside. Note that "80-odd people" is not qualified with ['at least 80'].
Approximation is also expressed by certain grammatically distinct constructions, as in [thirty or so] students (coordination) or [thirty-odd] students (affixation).
(Huddlestone and Pullum; The Cambridge Grammar of the English Language, p.431)
The hyphen is important in phrases such as twenty-odd people (= roughly twenty), to make it clear that we are talking about roughly twenty people, not a score of eccentrics. H. Fowler and J. Butterfield; Fowler's Concise Dictionary of Modern English Usage (2016)
More or less: sixty-odd dollars. Random House Dictionary
You use odd after a number to make it sound vague or approximate: She must be 50 odd by now. □ We received 500 odd replies. Harrap's Essential English Dictionary, p.640 (1966)
Hyphen can distinguish constructions such as ...30-odd professors (around 30 professors) and 30 odd professors (a convocation of eccentric educators). Lisa McLendon; The Perfect English Grammar Workbook, p.170 (2017)
III. Either more than or approximately the number indicated
[In combination] In the region of or somewhat more than a particular number or quantity. Lexico
[Postpositive] [In combination] In the region of or somewhat more than a particular number or quantity: She looked younger than her 50-odd years. Oxford New American Dictionary
From Sheila Dooley and Ferdinand de Haan; "On the nature of the approximative expression NUM-odd*" in William D. Lewis et al. (eds.) Time and Again: Theoretical Perspectives on Formal Linguistics (2009), which I found after posting my question:
It originated from the use of odd to denote a surplus or remainder, which usage has existed for several hundred years
Given that Terry Langendon taught at the University of Arizona from 1988 until 2005 (i.e. seventeen years), it is tempting to use the numeral twenty with an approximative measure, as in (1):
a. Terry taught at the University of Arizona for twenty or so years.
b. Terry taught at the University of Arizona for some twenty years.
c. Terry taught at the University of Arizona for twenty-odd years.
Although (1a) and (b) are perfectly fine, there is a problem with (1c): it seems unnatural to use the expression NUM-odd when referring to a number below NUM. The present paper is a study of the NUM-odd expression.
This expression may seem like a very infrequent type of phrase in contemporary English, but a corpus study shows that this is an illusion.
It is probably still the case that NUM-odd when combined with lower level numbers (the 'tens') expresses a range with NUM as the lower limit, especially when combined with nouns such as year (the prototypical instance). However, at higher levels, such as two thousand-odd the NUM-odd construction is turning into a true approximative and can be used in the sense 'about'.
Expressions like “twenty-odd years,” “a dozen-odd people,” and “two hundred-odd mistakes” are usually written with a hyphen before the “odd” to indicate that the exact number is unknown—perhaps a bit higher than the stated number. If you omit the hyphen, as in “a dozen odd people attended my birthday party,” you risk giving the impression that the people who came were odd rather than that you can’t be sure of the precise number of your guests. Paul Brians; Common Errors in English Usage (2013)
How would you know when -odd is being used to mean somewhat more than the number indicated, and what does that actually mean, since an approximate number may have been rounded up or down (or do some folks still always round down)?