It often appears in words related to speaking, calling, or sound:
* Vocal: relating to the voice
* Vociferous: loud and noisy
* Vocation: a strong feeling of suitability for a particular career
* Advocate: a person who publicly supports or recommends a particular cause or policy
* Evoke: to bring or call forth (a feeling, memory, or image)
* Invoke: to call upon (a deity, spirit, or power) for help or protection
* Provoke: to stimulate or give rise to (a reaction or emotion, typically a negative one)
So, when you see the root word "voc," think of it as relating to the act of speaking or making a sound.