Vivace is Italian for "lively" and "vivid". It is pronounced [viˈvaːtʃe] in the International Phonetic Alphabet.
Vivace is used as an Italian musical term indicating a movement that is in a lively mood (and so usually in a fast tempo). The speed typically coincides with that of "Molto Allegro" and implies a metronome marking of 132-160 if played 4 notes to a beat.
It is usually found on a piece of music, at the start or at the beginning of a new phrase.