Intonation is the way the pitch of a voice goes up and down when speaking. It is not used to change the meaning of a single word. Instead, it is used for other reasons, such as:
All spoken languages use intonation. But not all languages use pitch to change the meaning of a word. Languages that use pitch to change a word's meaning are called tone languages. In these languages, intonation still exists along with the tones for words.
Intonation is a main part of prosody. Prosody also includes rhythm, stress, and speed of talking. How something is said can be as important as the words themselves. Intonation gives extra meaning that is not in the written words.
Intonation has a few important jobs in speaking. Sometimes it does more than one job at the same time.
The best-known job of intonation is to show a speaker's feelings or attitude. A sentence can be understood as kind, not serious (sarcastic), happy, or angry just because of the pitch used.
Intonation helps show the grammar of a sentence. A common example is showing the difference between sentence types. In many languages, like English, this is the main way to make questions.
Intonation is used to put stress on the most important word in a sentence. The word that has the main change in pitch is the one that gets the focus. Changing the focus can change the whole meaning of what you are trying to say.
Intonation helps organize a conversation. It can show whose turn it is to talk, show if information is new or old, and group words into ideas. For example, a voice that goes up a little can mean a person is not finished talking. A voice that goes down shows they are done, and another person can speak.
Intonation happens because of changes in the fundamental frequency (F0) of the voice. We hear this as pitch. The F0 is how fast the vocal cords in the throat move back and forth. Speakers can control their vocal cords to make different patterns of pitch. These patterns are called pitch contours. These patterns are not random. They follow rules for each language or dialect.
It is important to know the difference between an intonation language and a tone language.
Tone languages also have intonation. The pitch for the whole sentence is put on top of the tones for each word. For example, asking a question in a tone language might still use a rising pitch at the end of the sentence. This changes the word tones a little bit.
Linguists (people who study language) have ways to write down and study intonation. An early way was to describe the main pitch change as a 'fall', 'rise', or 'fall-rise'.
A more modern way is called ToBI (Tones and Break Indices). It uses special marks to show high pitch (like H*) and how sentences end (like L-L% for a low-falling end). This helps linguists study pitch in a clear way.