In the term "song" there is a diphthong.
The term diphthong comes from the Latin diphthongus , which in turn has its origin in a word from the Greek language. The term refers to the meeting of a pair of different vowels that are expressed in the same syllable . For example: "song" , "dead" , "luck" .
For a diphthong to exist, at least one of these vowels must be weak . In Spanish, the weak vowels are i and u . The diphthong can therefore be formed by two different weak vowels ( «cuidado» , «diurno» ) or by a strong vowel and a weak one (although only in cases where the weak vowel is not stressed, otherwise the diphthong is broken).
Types of diphthong
If we are faced with the presence of a strong and a weak vowel, the diphthong can be rising (when the second vowel constitutes the syllabic nucleus) or falling (the syllabic nucleus is found in the first vowel).
Examples of rising diphthong are «piedra» and «pascua» , while examples of falling diphthong are «paisaje» , «pseudo» and «corticoide» .
In addition to these two types of diphthongs, it should be noted that there is a third type of diphthong, which is called a homogeneous diphthong. In this case, it is determined that it is characterized by beginning and ending with a closed vowel. This gives rise to two possible combinations: iu and ui.
"Piedras" is a word with a crescent diphthong.
Hiatuses and triphthongs
It is important to emphasize that when we refer to this set of vowels in terms of language, it is inevitable that we also refer to other types of union of these letters that, on occasions, can be confused with that one. Specifically, we are referring to hiatuses.
The aforementioned hiatuses are the union of two vowels that are pronounced in different syllables and therefore do not form a diphthong. More precisely, they are usually composed of a closed vowel and another strong vowel or two strong vowels.
In the first case cited, we would have as examples words such as país, púa, maíz, María or Raúl. As an example of what a hiatus composed of two strong vowels is, we would have the following terms: zoo, saeta, peón, teatro or poeta.
It should also be noted that when we talk about diphthongs and hiatuses, it is inevitable to refer to triphthongs. These are defined as the union of three vowels in a single syllable, more exactly the formula for them would be: closed vowel + open vowel + closed vowel. Examples of this are the words criáis, vieira, Mieira, riáis or asociáis.
Spelling rules related to diphthongs
There are several spelling rules related to diphthongs. The word y , when it appears at the end of a word , can form a diphthong (or even a triphthong) since it has a vowel value (it sounds like i ). For example: «Gualeguay» . If it is at the beginning of the word, or in the middle and retains its consonant property, it cannot form a vowel grouping ( «playa» ).
On the other hand, the silent h , which does not produce a sound, does not prevent the establishment of a diphthong even when it is placed between two vowels: «desahuciar» , «ahijada» .