Vowels can be long or short . In many languages of the world, tone plays an important role in distinguishing one morpheme from another. Notice that tone isn't the same as stress or intonation . All of these involve changes in the pitch of the voice. Stress, sometimes also known as accent, is the rise and fall of the pitch throughout the syllables of a word.
Intonation is the rise and fall of the pitch throughout the words of a sentence.
In the statement, the words have more or less even pitches with respect to each other. Tone is somewhat like stress in that it also is the rise and fall of the pitch throughout a word. However, tone is used to distinguish words that have the same sounds which may have unrelated meanings, while stress is not. Furthermore, the beginning pitch and the ending pitch of a tone is central to distinguishing words. Slightly different beginning or ending pitch means different words.