Spanish vowels are divided into two categories: hard and soft. Hard vowels (A, O, U) cause the consonant that precedes them to be pronounced with a hard sound, which I've abbreviated in this lesson as [HS], while soft vowels (E, I) are preceded by a soft sound [SS]. (Note that consonants – R, L, etc. – are always preceded by the hard sound.)
The consonants affected by this hard/soft distinction are C, G, and, to a lesser extent, Z.*
* The letter Z is a hard consonant, meaning that it Z has no "soft" pronunciation and, with very few exceptions, cannot precede an E or an I; it must be replaced by the letter C (as explained below).
Some Spanish words need a hard sound in front of a soft vowel, or a soft sound in front of a hard vowel. This is the reason behind many Spanish spelling changes in plurals and irregular verb conjugations (mostly in the preterite and subjunctive). For certain plurals and verb conjugations, it is necessary to change the spelling in order to maintain a hard sound in front of a soft vowel or a soft sound in front of a hard vowel.
|To make a hard sound in front of a soft vowel:|
|C –> QU||sacar –> yo saqué|
|buscar –> yo busqué|
|G –> GU||pagar –> yo pagué|
|jugar –> yo jugué|
|Z –> C||comenzar –> yo comencé|
|lápiz –> lápices|
|To make a soft sound in front of a hard vowel:|
|C –> Z||hacer –> él hizo|
|G –> J||coger –> yo cojo|
Please note that this lesson is only a guideline for the Spanish that I know, which is Castilian Spanish. There are many regional variations in Spanish pronunciation.