I have heard of the omission of some sounds and some clitics (pronouns and prepostions) that have shortened versions.
for instance τρώω → τρώ, οι οποίοι → οι οποι and αλκοόλ → αλκόλ. First of, is it correct to write them this way? and second, I have seen some ι's written but not pronounced like in χρησι̱μοποιώ. And then we have the shortened clitics:
-για → γι'
-σε and με (both as pronouns and prepositions) → σ' and → μ'
-από → απ' or → αφ' (should I know any difference between these two?)
As for me, I would use them before vowels, but I want to be sure of this as the course often counts them as wrong. I also want to know whether all of this doesn't sound to colloquial.
1.τρώ, οι οποι and αλκόλ are all grammatically incorrect, and do not sound proper in speech. The fact that there are double vowel cases like ώω, οίοι and ο doesn't mean the the two vowels become one. (maybe just sometimes, αλκόολ sounds like αλκόλ, but it's not grammatically accepted.) :P
2.Αll vowels are pronounced in χρησιμοποιώ, but I feel like someone would assume that ι right before μ isn't, because if the speaker speaks fast enough, the vowel sound is not clear but a bit "muted" instead. It's there though, it is pronounced, and it's not omitted. It just might sound a bit muted, depended on the situation.
3.As for the clitics:
Για becomes γι' when the next word begins with an α.
σε does become σ' when the next word begins with a vowel (σ'εσένα, σ' αγαπώ, σ' ολόκληρο τον κόσμο etc.), and same goes for με (μ' εσένα, μ' αγαπάς, μ' ένα παράπονο etc.).
(Take note here that σου and μου also become σ' and μ' (σ'αρέσει, μ' αρέσει), but not in all cases, and they are not interchangeable with με or σε. Μ' αρέσει - Μου αρέσει, and not Με αρέσει, Σ' το είπα - Σου το είπα, and not Σε το είπα. Στο είπα is a pretty common mistake, even for natives.)
Από becomes απ when the next word begins with a vowel, and most of the times, before the definite article's genitive and accusative case (απ' το, απ' την, απ' τον etc.).
Also, από becomes αφ' when the next word is a word that used to have a 'rough breathing accent' in the polytonic system (a δασεία, also known as spiritus asper in english.) But that case is pretty rare, in my opinion. The most common (if not the only) case of αφ' you'll probably come across is the phrase "αφ'υψηλού".
Ι think that's all the help I can offer. ^.^
Dimitra, I have an objection here. First of all, "σ' ευχαριστώ, σ' έχω βρει" are not examples of σου that becomes σ', it's still σε (we wouldn't say σου ευχαριστώ but σε ευχαριστώ, and σου έχω βρει would become σου 'χω βρει, σ' έχω βρει is σε έχω βρει). Με and σε are not only prepositions, but also the weak type of the personal pronoun in the accusative case. And even though Στο είπα is incorrect because the weak type of the personal pronoun cannot drop its vowel(s) without an apostrophe and become one with the following word (the weak type of the personal pronoun αυτό in this case), Σε το είπα and Με αρέσεις may be idiomatic and not so typical or formal or even "proper" but are not considered incorrect. In northern Greece many people use the accusative case of the personal pronoun (strong and weak type) rather than the genitive case. There is an interesting article of Babiniotis on the subject, which you can find in http://www.babiniotis.gr/wmt/webpages/index.php?lid=1=20=45
*For some reason when I save my post it changes the link, I don't understand what the problem is, I've tried to put spaces in the middle but still, I have the same problem. For the article, you can enter the website (Είσοδος at the bottom of the first page) and then it's in the unit of "Γλωσσικά & εκπαιδευτικά" with the title "με λέει μου λέει, με δίνει μου δίνει"
Yeap, I don't understand what's the issue here. In the notification mail that came to me for your comment, the link is complete and working, but here in the discussion, duolingo removes characters from the link and it doesn't. :/
P.S. I have a suspicion that maybe it's the & character that could be causing the problem, but I have no idea why this is happening.
Thank you for noticing this one about σου and μου, not sure why I sneaked two με/σε examples in there. o.o (I am a native speaker, so I can assure you it was by accident. :P)
Well, phrases like σε λέω/σε είπα might be a thing in Northern Greece, but we unfortunately can;t add them in the course, even if they are not incorrect, to avoid some potential confusion. I just thought it would be good to mention it in my post, just in case.
I assumed you're native speaker from your posts, and so am I. I figured that it must have been an oversight but since many learners read the posts to answer their queries or find some rules, I thought it would be useful to make it clear in case someone gets confused.
As for the idiomatic use of με/σε, of course I don't expect them to be added in the course, not only because it would cause confusion but also because it would be impossible to include every idiomatic word/phrase/word order/use of language in general, not to mention the literaty/poetic ones, or the archaic ones etc. But I thought I could mention it here in the discussion forum, so that if someone comes across this phenomenon they could recognise it, because when I listen to/read a native speaker of a language I'm learning and I see a type or a use I'm not aware of, I always wonder whether it's an acceptable idiomatic use or some colloquialism, or it's simply incorrect. Tbo, even though I'm born and raised in Thessaloniki, I hardly ever use με/σε that way - though I do say πάνε instead of πήγαινε for the 2nd sing. person of the imperative, and I can't seem to stop putting the causative conjunction αφού at the end of the clause. ;D
There is a good article in Wikipedia about the so called φθογγικές μεταβολές, https://el.m.wikipedia.org/wiki/Φθογγικές_μεταβολές a case that can be met in all languages, including English.
I don't think that one can learn all rules about, even being a native speaker. This phenomenon is to avoid χασμωδία=hiatus (?),that is to be easier to pronounce the words, euphony.
Some rules had put this site http://www.foundalis.com/lan/grphdetl.htm
The classic grammar book by Manolis Triantafyllidis contains detailed information about https://www.google.gr/url?sa=t=web=j=http://www.greek-language.gr/greekLang/files/document/modern_greek/grammatiki.triantafyllidi.pdf=0ahUKEwiM5uu166zUAhVFLhoKHWzCAI0QFggdMAA=AFQjCNEPh9p1UA1BnEOO2e6Vlar1jFAJDQ=9Ijm9aa5BP4sO9CPIsq5_Q ,in the pages 32-37 in the book, with many examples.
How one can solve this problem of tons of rules? I think it is practice, not rules.