I have little to share on this question. Nonetheless, I trust to have in depth analysis on the matter from learned colleagues. In addition, I have no doubt at all that colleagues will be magnanimous in providing where necessary, resource materials that will help my curious mind satisfy itself. Thank you all.

Diglossia refers to a famous essay by Charles Ferguson "Diglossia" (Word. Journal of the Linguistic Circle of New York. 15, 1959, 325–340). It refers to a society or an area where two languages are used. Bilingualism on the other hand means that an individual uses two languages; bilingualism can be combined with diglossia. Concerning language teaching the first approach is always bilingualism; dihlossia refers to the context, if the two languages are used in the environment, you can speak of diglossia.

I agree with Charles. The notion 'diglossia' means the language-situation of a certain region, where the speakers speak two languages and (I think this is important, too) normally use language A in other situations than language B.

Dear All

I thought that Diglossia meant that you can read the same word in two ways: if you write 'ghoti', you can read it as gh-as in ghost, o as in pot, ti as in tip; or you can read the same as fish, (as said by Shaw or someone else') gh as in laugh, o as the o in women, ti as in nation. This is a problem with languages having alphabets which do not have one is to one correspondence between written script and phonemes; ie most commonly in English (The above said example is for English; just 26 letters for so many phonemes), and less of a problem with Indian languages with alphasyllabaries; my language Malayalam has 52 letters of the alphabet +some geminates (Malayalam has the largest number of letters).

As to your question, a sociolinguist will say that both are right; one didactician will say one pronunciation is right and another didactician will say the other is right each arguing vehemently

Correct me if I am wrong

Narayanan

Pronounciation of the same word or letter in two ways I think is called dialect change.

Homograph is used to speak about two words spelled in the same way with two different meanings and pronociations, e.g. sow / saʊ / female pig vs. sow / səʊ / to plant or spread seeds in or on the ground.

This has nothing to do with either diglossia or dialect change.

The spelling ghoti for fish, is a creative respelling used as kind of a pun to show the need for an English spelling reform: gh=f like in laugh, o=i like in women and ti=sh like in nation.

Behind this lays the phenomenon that most graphemic systems are far away from being perfectly phonetic, meaning one letter sign represents one sound. Therefore a cluster of graphemes can represent only one phoneme and a grapheme can correspond to more than one phoneme, etc.

Dear Charles

I was wrong Charles and I stand corrected; I failed to verify before writing

Wikipedia "In linguistics, diglossia (/daɪˈɡlɒsiə/; Greek: διγλωσσία < δι- prefix denoting two, from δίς, twice + γλῶσσα, language + -ία, suffix denoting state or attribute, "speaking two languages") refers to a situation in which two dialects or languages are used by a single language community. In addition to the community's everyday or vernacular language variety (labelled "L" or "low" variety), a second, highly codified variety (labelled "H" or "high") is used in certain situations such as literature, formal education, or other specific settings, but not used for ordinary conversation"

By the way, Homography is same written form (same spelling), with or with out same pronunciation but different meanings; like in sow that you mentioned. But in the case of ghoti being read as fish, it is a case of same orthograph pronounced in two ways. It is not digraphia (Digraphia "using two writing systems for the same language"). Neither is it homophony, which is same pronunciation as another word but differs in meaning, and may differ in spelling, like rose (flower) and rose (past tense of rise); the sow you mentioned falls into this too. So what is the name for ghoti/fish where orthography is different, meaning is different but can be pronounced the same

Narayanan

PS. I gave you an upvote since you corrected me and I was wrong. But someone seems to have given you a downvote!

Harold F. Schiffman refers to Ferguson's seminal article (1959) in discussing the concept of diglossia in sociolinguistic situation. Ferguson originally summarized diglossia (1959: 435) as follows:

DIGLOSSIA is a relatively stable language situation in which, in addition to the primary dialects of the language (which may include a standard or regional standards), there is a very divergent, highly codified (often grammatically more complex) superposed variety, the vehicle of a large and respected body of written literature, either of an earlier period or in another speech community, which is learned largely by formal education and is used for most written and formal spoken purposes but is not used by any section of the community for ordinary conversation.

The notion that diglossia could also be used to characterize other multilingual situations where the H and L varieties were not genetically related, such as Sanskrit (as H) and Kannada (as L) in India, was developed by Fishman (1967) and research on diglossias since have focused to a great extent, though not entirely, on characterizing various kinds of extended diglossias.

Post-1959 research on diglossia has concentrated on a number of variables and important questions: function, prestige, literary heritage, acquisition, standardization, stability, grammar, lexicon, phonology, the difference between diglossia and standard-with-dialects, extent of distribution in space, time, and in various language families, and finally what engenders diglossia and what conditions favor its development.