Final answer:
The prefixes that indicate joining or being fused include 'con-', 'com-', 'syn-', and 'sym-'.
Step-by-step explanation:
The prefix that means joined or fused is often represented by con-, com-, syn-, or sym-. These prefixes indicate that something has been brought together or combined. For example, in the process of assimilation during word formation, certain letters in prefixes may change to resemble the initial letter of the word it is prefixed to, like 'com-' changing to 'col-', as in the word collaborate. This indicates a blending or joining of efforts.