A tone language or tonal language is a language in which saying words with different "tones" (which are like pitches in music, but not as many) will change the meaning of the words, even if the pronunciation of the word is the same otherwise.
Many languages that people in Asia speak are tone languages, such as Chinese, Vietnamese, Thai, and Punjabi. But most languages, including those that come from Europe like English, are not tone languages at all. But in some of these, pitch accent is important. That means a word's meaning could be different depending on which syllable is stressed. Examples include Swedish, Norwegian, Serbo-Croatian, Lithuanian, and some Asian languages like Japanese. However, pitch accent is not the same as tones.
Some tones may sound alike to people who do not speak a tone language, and can be easy to forget. They are the most difficult part of learning a tone language for many people.
In Mandarin, the sentence ma ma ma ma (麻媽罵馬) includes four different words. If we add numbers to identify the tones, it can be written ma2 ma1 ma4 ma3, which means "the hemp's mother scolds the horse." Some ways of romanization write each tone with a different spelling; ma2 ma1 ma4 ma3 in Pinyin would be written ma mha mah maa in Gwoyeu Romatzyh romanization. Most use numbers or accent marks (mā má mǎ mà in Pinyin). There is a poem called Lion-Eating Poet in the Stone Den (施氏食獅史). It has 92 characters in it which are all read the same way in Mandarin ("shi") but have different tones.
Mandarin does not have many syllables. For instance, the words for "mother," "hemp," "horse," "scold," and a word put at the end of sentences to make them into questions are all pronounced "ma." For "mother," you say "ma" high and level. For "hemp," you say "ma" starting low and ending high. For "horse," you say "ma" starting fairly high, dipping very low, and then going back up again. For "scold," you say "ma" starting high and ending low. To make a question out of a statement, you add "ma" but keep it very soft and short, and about on the same level. Mandarin has "first tone," "second tone," "third tone," "fourth tone," and "neutral tone." Other Chinese dialects have more tones, some as many as twelve.
Vietnamese and Pinyin use accents (diacritics) as the tone marks for the Latin script. Each marking defines an altered sound for the syllable. Most syllables only have one tone marking. But the letters in the syllable can be altered by other special character/letter markings. Syllables usually form one word in un-hyphenated compound words. Pinyin may have style differences that break from convention (in use) because it is a demonstration language. Vietnamese has a national script that always follows the syllable marking style.
Tone language Facts for Kids. Kiddle Encyclopedia.