Editing Tone (linguistics) (section)

===Tone terracing===
{{main|Tone terracing}}
Tones are realized as pitch only in a relative sense. "High tone" and "low tone" are only meaningful relative to the speaker's vocal range and in comparing one syllable to the next, rather than as a contrast of absolute pitch such as one finds in music. As a result, when one combines tone with sentence [[prosody (linguistics)|prosody]], the absolute pitch of a high tone at the end of a [[prosodic unit]] may be lower than that of a low tone at the beginning of the unit, because of the universal tendency (in both tonal and non-tonal languages) for pitch to decrease with time in a process called [[downdrift]].

Tones may affect each other just as consonants and vowels do. In many register-tone languages, low tones may cause a [[downstep]] in following high or mid tones; the effect is such that even while the low tones remain at the lower end of the speaker's vocal range (which is itself descending due to downdrift), the high tones drop incrementally like steps in a stairway or [[Terrace (agriculture)|terraced]] rice fields, until finally the tones merge and the system has to be reset. This effect is called [[tone terracing]].

Sometimes a tone may remain as the sole realization of a grammatical particle after the original consonant and vowel disappear, so it can only be heard by its effect on other tones. It may cause downstep, or it may combine with other tones to form contours. These are called [[floating tone]]s.