Final answer:
The bolded word group, "tsunamis are enormous ocean waves," is a phrase.
Step-by-step explanation:
A tsunami is a series of ocean waves with extremely long wavelengths and high energy, typically caused by underwater earthquakes, volcanic eruptions, or underwater landslides. These waves can travel across entire ocean basins and cause significant destruction when they reach coastlines.
The bolded word group, "tsunamis are enormous ocean waves," is a phrase. A phrase is a group of words that functions as a single unit within a sentence but does not have a subject and a predicate, which are characteristics of a clause. In this case, the phrase provides additional information about tsunamis and their characteristics.