In English, when people say a “th” sound instead of an “s” sound, they have a lisp. A lisp is a speech impediment; it means that the person is mispronouncing words with “s” sounds.
English speakers often hear Spaniards speak and assume they have a lisp. However, not all Spaniards have a speech impediment. They just have different rules for the pronunciation of the letters c, s and z than other versions of Spanish. (Note: in this lesson we will be discussing c when it is used before an i or e; in other uses, like in the word “casa,” the c makes a “hard c” sound like the English letter k)
Most Spanish classes, at least in the United States, teach students that the letters c, s and z are pronounced like the English s (with some exceptions, of course).
So, the c and the s in gracias and the z in azul all sound like the s in the English word sad.
In Spain, there are three different ways of pronouncing c, s and z. The words casar (to marry) and cazar (to hunt) are helpful in explaining the differences between the three groups.
Seseo is the pronunciation used in some parts of Spain and almost all of Latin America. The c, s, and z are all pronounced like an English s. A person in the seseo group will pronounce the words casar and cazar the same, with an English s sound in the middle of the word.
Ceceo (pronounced with “th” sounds for both c’s) is common in some parts of southern Spain. The c, s, and z are all pronounced with an English “th” sound. In other words, there is no English “s” sound in this variation of Spanish. The words casar and cazar are pronounced the same, with a “th” sound in the middle of the word. To native English speakers, ceceo sounds like a lisp.
Distinción is a combination of seseo and ceceo. The s is pronounced like an English s (seseo), while the c and the z are pronounced like a “th” (ceceo). Someone who speaks with distinción will pronounce casar with an English s sound and cazar with a “th” sound.
In reality, Spaniards don’t usually lisp! However an untrained listener might think that someone who speaks with ceceo or distinción has a speech impediment. Now, you can take this knowledge and educate your friends!