While some may see having a lisp as some sort of haute novelty fit for the po-mo metrosexual way of life, it is actually an oral problem suffered by many people in the world. When you were a child just learning to talk, you may have lisped or stuttered; in fact, your relatives probably considered it cute. If you're a teen who is still stuttering, though, you may not feel like it's so endearing. You're not alone. More than 3 million Americans have the speech disorder known as stuttering (or stammering, as it's known in the United Kingdom). It's one of several conditions affecting a person's ability to speak clearly.

Articulation disorders encompass a wide range of errors people can make when talking. Substituting a "w" for an "r" ("wabbit" for "rabbit"), omitting sounds ("cool" for "school"), or adding sounds to words ("pinanio" for "piano") are examples of articulation errors. Lisping refers to specific substitution involving the letters "s" and "z." A person who lisps replaces those sounds with "th."

It's easy to take the ability to speak for granted, but producing fluent speech without errors (speech that flows smoothly and is easily understood) is actually a highly complicated process. When we speak, we must coordinate many muscles from various body parts and systems, including the larynx, which contains the vocal cords; the teeth, lips, tongue, and mouth; and the respiratory system. Normal speech may seem effortless, but it requires precise timing, nerve, and muscle control. The ability to understand language and produce speech is coordinated by the brain. So a person with brain damage from an accident, stroke, or birth defect may have speech and language problems. Apraxia is thought to be due to a brain impairment that may or may not show up on brain magnetic resonance imaging (MRI) tests.

Some people with speech problems, particularly articulation disorders, may have hearing problems. Even mild hearing loss may have an impact on how a person reproduces the sounds they hear. Certain birth defects, such as a cleft palate, can interfere with a person's ability to produce speech. When a person has a cleft palate there is a hole in the roof of the mouth, which affects the movement of air through the oral and nasal passages. There also may be problems with other structures needed for speech, including the lips, teeth, and jaw.

Genetics may also play a role in some speech problems. For example, stuttering seems to run in some families. But in most cases, no one knows the exact cause of a person's speech problems.