I've noticed that in Italian, besides è and é, which are pronounced differently (the first with the mouth more open than in the second case, thus producing different sounds; examples include the very frequent words
è which means
he/she/it is and
perché which means
why or because), the only other vowel which can take both diacritics is o (ò and ó) which can also be pronounced in two ways with the mouth more open in the former case and with the mouth more closed in the latter case. The other three vowels can only take one accent which by convention is written in most texts as a grave accent (thus à, ì, and ù) and in any case take only one pronounciation. From what I've seen on the Internet it appears as though á is not part of Italian orthography whereas í and ú are not part of the most common, conventional, written Italian orthography. The letter a with an acute accent on top never appears and is not valid anywhere in Italian text. On the other hand, some Italian publishing companies write í and ú in a somewhat unconventional manner in place of ì amd u throughout the entirety of some of their texts. Thus, when writing, one must make a decision as to whether to follow the most common convention of spelling ì and ù throughout the text, or the unusual convention of spelling í and ú throughout the text.
In Italian it is possible to produce both open and closed sounds corresponding to the Italian vowel
o which may be written with or without diacritics / accent marks. Here are just a few of the most common examples: the word
però (which means
but) is pronounced as an open oh, just as the verb
ho (which means
I have) which is also pronounced as an open oh (the h in front of the oh is silent here), but the word
o (which means
or) is pronounced as a closed oh.
Nevertheless, I am also not sure where 'ó' would be used, but Wikipedia lists it. Quoting from the
Accento acuto section of the Italian Wikipedia:
L'accento acuto è presente in molte lingue per indicare una particolare intonazione su diverse vocali:
- lingua italiana: sulla vocale é, ó, ma anche, nelle scritture più ricercate e forti di una solida base fonetico-linguistica, sulle vocali í, ú
Interestingly enough, Wikipedia also references this paper on the subject matter.
As pointed out by @Charo below, accent marks are always used to denote stress, but with "e" and "o" they also tell you how to pronounce the vowel.
So, how can I decide whether to write plain
o, when to write
ò, and when to write
ó, and what is the exact difference between these?