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 the diphthong to exist, one of these vowels (at least) must be weak . In the Spanish language, the weak vowels are i and u . The diphthong, therefore, can be formed by two different weak vowels ( "careful" , "daytime" ) or by a strong and a weak vowel (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 increasing (when the second vowel constitutes the syllabic nucleus) or decreasing (the syllabic nucleus is found in the first vowel).
Examples of increasing diphthong are "stone" , and "easter" , while examples of decreasing diphthong are "landscape" , "pseudo" and "corticoid" .
In addition to these two types of diphthongs, it must be made clear that there is a third modality called homogeneous diphthong. In this case, it is determined that it is the one that is characterized because it begins and ends with a closed vowel. This gives rise to two possible combinations therefore: iu and ui.
«Stones» is a word with a growing diphthong.
Hiatus and tripthongs
It is important to emphasize that when we refer to this set of vowels in language, it is inevitable that we also make known other types of union of these letters that, sometimes, 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, those are usually composed of a closed vowel and another strong vowel or two strong ones.
In the first case cited, we would have as examples words such as country, púa, corn, María or Raúl. As an example of what a hiatus composed of two strong vowels is, we would have the following terms: zoo, arrow, pawn, theater or poet.
Likewise, it must be made clear that when we talk about diphthongs and hiatuses it is inevitable to refer to what tripthongs are. These are defined by being the union of three vowels in a single syllable, more precisely their formula would be: closed vowel + open vowel + closed vowel. Examples of this are the words criáis, scallop, Mieira, riáis or associate.
Spelling rules related to diphthongs
There are various spelling rules linked to diphthongs. The y , when it appears at the end of the word , can form diphthong (or even tripthong) since it has a vowel value (it sounds like i ). For example: "Gualeguay" . If it is at the beginning of the term, or in the middle and retains its consonant property, it cannot form a vowel grouping ( "beach" ).
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 in the middle of two vowels: "desahuciar" , "goddess" .