What are the added sounds between words when a sentence is spoken?
When listening to the whole sentence, as compared with listening only to the individual words, there are often added sounds like "ton", "ten", "on" or "en" between the words. What are these? Why are they not written out? Is it a feature that only occurs in certain arabic dialects?
I think you are talking about "Tanwin" and it's 3 types, Tanwin al-fatha, Tanwin aD-Damm, Tanwin al-kasr. Tanwin is somewhere between a vowel and a suffix.
Note that, al-fatha, aD-Damma & al-kasra are short vowels known as diacritic signs, and they are symbols written either above or below a particular consonant.
Tanwin is represented by a double fatha, double Damma, or double kasra (Two of the same diacritic sign) over the top of the consonant it follows in pronunciation.
Examples: The word شكراً pronounced “Shukran”, which means “Thank You” (Notice "an", now we don't have a "ن" (Consonant N) in شكراً but we pronounce it because of Tanwin al-fatha
The word أٙبٌ pronounced “Abun”, means “Father” what makes us say "Abun" and not "Ab" are simply those diacritic signs (double Damm) above "ب"
I tried to make it as simple as possible, if you have any questions, let me know.
I'm also not sure if this is Tanwin. Unless Tanwin is sometimes applied without being written out? An example is the sentence:
رانْيا امْرَأة عَرَبِيّة
Where after the first two words there is an added "ton" or "on" when the whole sentence is spoken. I thought it was perhaps a way to avoid having two vowel-sounds next to each other, and/or to demarcate the beginning of a new word.
Tanwin can be applied without being written out indeed, in fact that applies to all the diacritic signs. They are not used in normal Arabic writing and are left out, because they are distracting and unnecessary for anyone that has already learned to read correctly according to the context.
Ok, great. It seems Tanwin is the explanation then. The only thing I am still confused about is that Tanwin as you and duolingo has described it (although Duolingo didn't mention the word "Tanwin") only seems to be an "an"-sound, which hasn't explained the "tan"-sounds. By googling I eventually found this, which explains the "tan"-sounds: There are 3 types of tanwin تنوين word endings In Arabic.
Marfu مرفوع sounds like dun or دٌ Example محمدٌ
Majrur مجرور sounds like din دٍ example محمدٍ
Mansub منصوب sounds like Dan دً example محمداً from https://learnquranicarabic.wordpress.com/2010/07/26/three-types-of-tanwin/
Are these other types of Tanwin?
You know the letter "taa" "ت" right? it's called "تاء مبسوطة" "taa mabsuuTa" which translates to (flat taa)
Well, "ة" is just another variant of it, called "تاء مربوطة" "taa marbuuTa" it translates to (tied taa)
This variant can ONLY be found at the end of a word. حمزة. كلمة. جميلة... When not pronounced, It basically just serves as the short vowel "a" And it indicates femininity, meaning all words with "ة" are feminine words.
When do we pronounce it?
Single word level wise, and at the end of a sentence, it's usually silent, or pronounced as a 'h' sound طاولة Taawila / Taawilah جميلة jamiila / jamiilah
Sentence level wise, and when the word with a "ة" is in the middle of a sentence, then it's not silent and pronounced according to the context and diacritic signs if shown. Look at طاولة in this example:
هذه طاولة جميلة This is a beautiful table
"haaðihi Taawilatun jamiilatun"
"haaðihi Taawilatun jamiila(h)"
Nope, they're just three,
Marfu (I referred to as Tanwin aD-Damm) Majrur (Tanwin al-kasr) Mansub (Tanwin al-fatH)
In other words they're "un", "in" & "an" But, these are suffixes that's why you hear "dan" "kun" or "tan" etc depending on the last letter of the word concerned and the type of diacritic signs of Tanwin it has.
I asked a native speaker of Iraqi Arabic (a poll with a sample size of 1). He said that the sentences sound like Syrian Arabic, and an older form of Arabic. He said that in some countries this form of speech sounds old and outdated. If you want an example of some of the pronunciation differences between types of Arabic, you may be interested in Mango (https://mangolanguages.com/) which includes Egyptian, Labanese, Iraqi, and Modern Standard versions of Arabic