Final answer:
The prefix meaning "together" is both 'Sym-' and 'Syn-' as in words like sympathy and synthesis, representing the coming together or unity in various contexts.
Step-by-step explanation:
The prefix meaning "together" is both Sym- and Syn-. These prefixes are used in words to indicate a coming together or unity of different elements. For instance, in the word sympathy (Sym- + pathy), the two 'c's in sympathy come from the prefix and the stem, respectively, combining to denote a feeling of compassion or sorrow for the troubles of another person. Another example is the word synthesis (Syn- + thesis), where the prefix Syn- indicates the combination or integration of ideas to form a theory or system.