Word for something which isn't what it seems to be
I recently started learning French and am confused by its pronunciations. The main problem being that the words never seem to sound the way they're written - isn't what it seems to be! (I know English isn't any better, but criticisms of my observations are safely off-topic here!) I need a word which indicates this deceptiveness/inconsistency while not sounding too negative. Because I still am fascinated by French.
For example, here's something I'd like to say: Oh french, you ____________ beauty!
So it really cant be too negative, unless you think the following word "beauty" makes for an amusing/endearing oxymoron. Then if the overall sentence doesn't sound too negative, I'm willing to accept any word.
The Oxford Dictionaries site offers as a definition of "inconstant" the following: "Frequently changing; variable or irregular". Synonyms suggested include fickle, wayward, capricious, volatile, flighty, erratic, mutable, mercurial, and irregular. Any one of these could fill the blank in your sentence.
If you want to emphasize that you are frequently tricked into using the wrong pronunciation, perhaps cozening. It's a fairly rare, old-fashioned word that sounds friendly and cozy, but to cozen actually means
a. trans. To cheat, defraud by deceit.
a. To deceive, dupe, beguile, impose upon.
To beguile or cheat into, up, etc.; †to induce by deception to do a thing.
("cozen, v." OED Online. Oxford University Press, September 2016. Attestations and some additional sub-definitions omitted.)
As suggested by the third definition, cozen and cozening often have connotations of seductiveness, which seems especially apropos for something that is fascinating and beautiful but leads you into error. For example:
No courtesan! Hast thou deceived me then? Tell me, thou wicked-honest cozening beauty! Why didst thou draw me in with such a fair pretence, why such a tempting preface to invite, and the whole piece so useless and unedifying? (Aphra Behn, The Feigned Courtesans, originally staged 1679)
I never did believe in your false face,/I knew you well in every other thing,/But your fine eyes shone with so bright a grace,/Your features were so sweet and cozening,/That to your promises my hopes would cling;/My soul believed in them; and for this I die. (Alistair Moffat, Tuscany: A History, 2011; translating from Italian)
He was in a manner tricked, coney-caught, a court-dor to a cozening cotquean. (Anthony Burgess, Nothing Like the Sun, 2013)
So, in your phrase:
Oh French, you cozening beauty!
Note that this is a fairly archaic term; although it is still in use, it definitely has an old-fashioned feel, and some of the recent usages which I've seen don't appear to understand the connection to deception. For your purposes, these facts may be somewhat in the term's favor, as they may somewhat mitigate the negative connotations.
For a more alliterative phrase, beguiling beauty has a nice ring, though I think the connotations of deceptiveness are less clear there.