言语障碍（Speech and language impairment），是包括听觉、说话的能力、语言能力等等沟通问题的总称。听觉问题一般会交由耳科医生处理，而言语治疗师则负责治疗一个人的说话及语言能力。第一大类是发音问题（Speech disorder），包括构音问题（articulation）：无法运用嘴唇、舌头及口腔构成正确的辅音或元音；语音问题（voice）：难以控制声带，以至难以控制声音的高低或音量；以及流畅问题（fluency）：无法以正常的速度流畅地说话，或无法适当地强调音节。第二大类是语言障碍（Language disorder），包括无法将字词组合起来运用，无法掌握文法的规则等等。当中的原因是语义学及语用学研究的课题。

Speech and language impairment are basic categories that might be drawn in issues of communication involve hearing, speech, language, and fluency.

A speech impairment is characterized by difficulty in articulation of words. Examples include stuttering or problems producing particular sounds. Articulation refers to the sounds, syllables, and phonology produced by the individual. Voice, however, may refer to the characteristics of the sounds produced—specifically, the pitch, quality, and intensity of the sound. Often, fluency will also be considered a category under speech, encompassing the characteristics of rhythm, rate, and emphasis of the sound produced