Final answer:
Prefixes like syn- and com- have similar meanings, signifying 'together' or 'with', and under assimilation, similar prefixes are known to change their form for fluent pronunciation, such as ad- to ar-.
Step-by-step explanation:
Pairs of prefixes that have the same or similar meanings include syn- and com-, as they both carry the meaning of 'together' or 'with'. Assimilation occurs when prefixes are attached to stems and their final letters change to allow a more fluent pronunciation.
For example, when ad- combines with a stem that begins with an , it assimilates to ar-, as seen in the assimilation from ad- + rigo to ar-rigo. Similarly, the assimilation process is observed in com- + rade becoming comrade, as the double letters are a result of such prefixes preceding the letter 'r'.