You have several options here.
If you wish to be very proper, you should pronounce
just as you would
without the apostrophe. This comes closest to respecting the author's
intention, although it may sound funny to the modern ear. This is
because the preferred spelling nowadays for the possessive form of a
singular proper noun, as in
I got into Mavis's car,
is to add the extra "s", although some corporate style guides still
recommend or require dropping it. See, for example, the rules of
Associated Press (AP) style.
SINGULAR PROPER NAMES ENDING IN S: Use only an apostrophe:
Achilles? heel, Agnes? book, Ceres? rites, Descartes?
theories, Dickens? novels, Euripides? dramas, Hercules?
labors, Jesus? life, Jules? seat, Kansas? schools,
Moses? law, Socrates? life, Tennessee Williams? plays,
fredericksburg.com: AP Style: possessives
This contradicts Strunk and White's Elements of Style, which is
required reading at many universities.
Form the possessive singular of nouns with 's.
Follow this rule whatever the final consonant. Thus write,
the witch's malice
This is the usage of the United States Government Printing Office
and of the Oxford University Press.
bartleby.com: Strunk's The Elements of Style: Elementary Rules of Usage
The conflict between Strunk and the AP has been noted elsewhere.
possessives -- The main AP exception to Strunk and White's
Elements of Style involves forming the possessive of a
singular proper noun that ends in "s." AP says merely add an
apostrophe. Examples: Otis' cookies, Amos' ice cream, Charles'
chips. And here's a reminder of something I'm sure most of
you already know: To make something that is singular into a
possessive, add 's; to make something plural into a possessive,
first make sure it is plural, usually by verifying that it ends
in an "s," and then add an apostrophe. Here's a nonsense sentence
that illustrates the idea: One dog's bone is worth two dogs' ears.
Utah State University: Michael S. Sweeney: Guide to AP style
There's also the opposite case: when a singular noun ends in
s. That's a little trickier. Most style guides prefer s's:
James's house. Plain old s-apostrophe (as in James' house)
is common in journalism, but most other publishers prefer
James's. It's a matter of house style.
Rutgers University: Jack Lynch: Guide to Grammar and Style
In your own writing, then, you may regard the choice of
as a matter of preference. Do note that the latter is the more common
usage today, especially when the writing is informal, while the former
is regarded even by many of its adherents -- such as me -- as somewhat
But to return to the question of pronunciation, the way you say out
loud the possessive form of "Mavis" should match the way you prefer to
write it. If you fancy
in writing, then in your speech it should sound like a plural
construction, so that it rhymes with
If, however, you insist on the AP style, or if you are reading out
loud something written in that style, the orthodox practice is to
pronounce the word as though it were uninflected.
An acceptable alternative, which several English teachers of mine have
employed, is to pronounce
with an emphasis on the final "s", as an auditory hint of the
apostrophe. The emphasis consists not in stressing the final syllable,
but in extending the sound of the "s" to make it a slightly but
perceptibly longer hiss. You may think of it as
and certainly not
Also take note that when reading out loud a text in which
occurs, you would be doing the author a disservice if you pronounced
it to rhyme with
even if your own preferred usage is
In summary, you are free in your own writing to construct the
possessive of "Mavis" using either of the two accepted forms, although
you should follow the same usage consistently within a single
document. If you write "Mavis's", you should pronounce it to rhyme
with "Davises". If you write "Mavis'", read it as simply "Mavis" or
with added emphasis as "Maviss". If you are reading out loud the
"Mavis'" that someone else has written, respect the author's intention
by not pronouncing it as "Mavis's", but as either "Mavis" or "Maviss"
according to your preference.
P.S.: I have seen writers dodge this question by routinely using a
different construction. For example, Saki writes "aunt of Clovis"
instead of trying to form the possessive of his protagonist's name. A
friend of mine who is a stage actor does the same in speech.