The Diphthong

Let's say it right away, the diphthong is one of the greatest difficulties in Spanish. The diphthong is a complex vowel (two vowels in a row) that changes in sound when pronounced. This allows the pronunciation to be softened before the stronger vowels which are -a, -e and -o. The -i and -u soften the sound. An example is pensar: yo pienso, nosotros pensamos. *penso would be much too difficult to say and would risk masking the tonic accent on the o. A weakening is then added to the e to maintain good sound quality. For pensamos, there is no problem, the stress being on the a. Therefore no diphthong is needed. Note that in conjugation, we speak of diphthongization.

As we can see, the diphthong depends on the type of verb and tenses. This is what makes it particularly difficult. Here is a table summarizing the main diphthongs and other irregularities when they can still be classified: