"Dic" is the stem of the verb "dicere", which means "to say" or "to speak".
Here are some examples of how "dic" is used in Latin words:
* dictum: a saying or a proverb
* diction: the style of speaking or writing
* dictare: to dictate
* dictionarium: a dictionary
* predict: to say beforehand
While "dic" does relate to speaking, it's not the word itself that means "to speak". It's the stem of the verb "dicere", which does mean "to speak".