Voice Onset Time (VOT) is the duration of the period of time between the release of a plosive and the beginning of vocal fold vibration. This period is usually measured in milliseconds (ms). It is useful to distinguish at least three types of VOT which are shown in the schematic diagram below:
Zero VOT: where the onset of vocal fold vibration coincides (approximately) with the plosive release
Positive VOT: where there is a delay in the onset of vocal fold vibration after the plosive release
Negative VOT: where the onset of vocal fold vibration precedes the plosive release
