(Note this answer was previously posted to a question which has since been deleted on Programmers.stackexchange.com)
The abbreviated form char, short for character, can be pronounced in several different ways in American English: here's how you represent the various pronunciations in American English using the International Phonetic Alphabet:
- char as in char-broiled: /tʃɑr/
- char as in car: /kɑr/
- char as in character: /kær/
- char as in care: /kɛr/
For many speakers of American English (including myself), the /æ/ sound before /r/ is merged with the /ɛ/ sound. That is, the words marry and merry are pronounced the same. For these people, #3 and #4 are indistinguishably pronounced like #4. People with this merger are often confused if someone else tries to explain the distinction between #3 and #4.
I have heard all these forms used and as a descriptivist, I would make no attempt to declare any as “correct”. Each has different arguments for and against, which I will enumerate below.
- This form has the advantage of being “obvious”—that is, it is pronounced the way a naïve pronunciation of an unknown English word would be pronounced. It is also how the unrelated but identically spelled verb char is pronounced. On the downside, it preserves neither the initial /k/ sound nor the vowel of the word the abbreviation is derived from, character.
- This form maintains the initial /k/ sound from character but is otherwise pronounced as spelled. It does not preserve the vowel from character.
- This form maintains both the initial /k/ sound and the vowel from character. It is the most faithful to the source word. On the downside, /ær/ is not a phonotactically valid way for a word to end. The sequence /ær/ is only possible if there are additional vowels, as in marry or character. That is, if you say /kær/ as an independent word it is a violation of the normal phonotactic constraints of spoken English. Furthermore, it is a completely non-obvious pronunciation if you don’t already know that char is short for character and how character is pronounced.
- This form is very similar to #3, being quite faithful to the underlying form, but with the advantage of not violating the phonotactic constraint against words ending in /ær/. For people with the marry–merry merger, it is not actually perceived to be different from #3 at all. On the downside, it is a completely non-obvious pronunciation if you don’t already know that char is short for character and how character is pronounced. Also, if you do distinguish #3 and #4, then #4 does not actually have the same vowel as character.
Each possible pronunciation has its own set of advantages and disadvantages, which is why there is a diversity of pronunciation in the field—there is no form that is clearly better than all the others. Furthermore, the different possibilities are bound up in a dialectical difference that most speakers of American English are unaware of, so when discussions of how to pronounce char come up, often two people are talking about dialectical differences when what they think they are talking about is a lexical difference.