This section gives technical details that weren't covered in the Intermediate section, about sounds that were covered.
Gemination is the lengthening or shortening of vowels. This means that they are pronounced for longer. This can be applied to any vowel. Consonant gemination is a distinction made by some languages (for example Italian and Classical Arabic) where a single consonant is distinguished from a double "geminate" consonant. They mostly occur in intervocalic position (Swedish is unusual for its final geminates). Most languages only allow some of their consonants to be geminated.
Diphthongs are complex sequences of vowels which are made of two vowels pronounced next to each other. They are contrasted from "flat" vowels in many languages. They are made of an on-glide or an off-glide vowel as well as an obligatory nucleus whereas a "flat" "pure" vowel would only be made of a nucleus. Most common on-glides/off-glides are the vowels [i] (realized as [j] when it's a glide) and [u] (realized as [w] when it's a glide). Occasionally, some languages features triphthongs made of both an on-glide and an off-glide (examples: [jaj] or [jew]). They must not be distinguished from hiati which are sequence of vowels separated by a syllable break (example: [ej] would be a diphthong whereas [e.i] would be a hiatus, French distinguishes <paye> [pej] "pay" from <pays> [pe.i] "country").
Suprasegmentals are distinctions that apply not to one phoneme but to a whole syllable or word. Notable suprasegmental features are:
-stress (applies to a specific syllable of a whole word)
-intonation (Few languages make complex intonation distinction however some languages make simple intonation distinction such as Spanish and French which use it to distinguish statements from questions)
-juncture (where a syllable break occurs, often distinguishes multiple words from one, example in English are <a name> [a.nejm] and <an aim> [an.ejm]) -tone
-vowel and consonant harmony, the latter being relatively rare (a separation in group of different phonemes and the exclusive use of one of those group to form a word, for more information see the section "Vowel Harmony" below)
-mora (the use of distinctive syllable's weight which determines stress, timing)
This feature is common in agglutinative languages, i.e. in languages where one suffix represents one property (Turkic, Mongolian, Finnish, Hungarian). All vowels are divided in two groups (back vowels and front vowels), and only vowels from one group can be used in the word; therefore all suffices have two forms.
For example, in Tatar language the groups are following:
First group (Back vowels): a, ı, í, o, u Second group (Front vowels): ä, e, i, ö, ü
Plural suffix has forms lar and lär. The word for friend is dus, so friends is duslar; the word for house is öy, therefore, houses is öylär.
Sometimes there are neutral vowels that belong to both groups, like i and e in Finnish:
First group (Back vowels): a, o, u, e, i Second group (Front vowels): ä, ö, y, e, i
Usually group is selected by the kind of vowels in the root of the word. But in Chukchi language, for example, there are dominant and recessive group, and all vowels from recessive group are replaced with their dominant counterparts when a suffix with a dominant vowel is used.