Pitch is the rise and fall of our voice when we speak, sometimes called "highness" or "lowness." We use pitch to  gives subtle meaning to sentences. The use of pitch is called intonation, but the words "pitch" and "intonation" are often used interchangeably.

Pitch is directly related to word and syllable stress. Content words--the words that give us the picture of what is happening--are stressed more during speech than function words--the grammatical words of the sentence. With pitch, one or more of the stressed content words of our speech will have a more dramatic rise of pitch than the other content words, and that pitch change falls mostly on the stressed syllable of that content word. 

English speakers mark words with a higher pitch for many reasons, including:

  1. to make a simple statement (neutral statement)
  2. to contrast or clarify information
  3. to give new information
  4. to show emphasis
  5. to ask questions

For the purpose of learning English, pitch can be simplified to 4 levels:

'4-pitch' is the highest level of pitch and is used when the speaker wants to emphasize something, make a contrast, or show strong feelings. '3-pitch' is the usual level of the primary word of a thought group, and is most commonly the highest pitch of a thought group. '2-pitch' is the neutral pitch, and often used at the beginning of a thought, and '1-pitch' is the pitch a speaker often falls to at the end of a thought.

It is important to note also that a speaker's pitch travels slightly up and down from these levels throughout a thought group and with nearly every word. Also, these levels are relative; each speaker has a slightly different pitch for each level.