Some common synonyms of perpetual are constant, continual, continuous, incessant, and perennial. While all these words mean "characterized by continued occurrence or recurrence," perpetual suggests unfailing repetition or lasting duration.

// a land of perpetual snowfall

The synonyms perennial and perpetual are sometimes interchangeable, but perennial implies enduring existence often through constant renewal.

// a perennial source of controversy

In some situations, the words incessant and perpetual are roughly equivalent. However, incessant implies ceaseless or uninterrupted activity.

// annoyed by the incessant quarreling