Synonyms: continual, continuous, ceaseless, constant, incessant, perpetual, eternal, perennial
These adjectives mean occurring without stopping or occurring repeatedly over a long period of time. Continual is often restricted to what is intermittent or repeated at intervals: The continual banging of the shutter in the wind gave me a headache. But it can also imply a lack of interruption, the focus of continuous and ceaseless: The fugitive was living in a state of continual fear. The police put the house under continuous surveillance. We listened to the ceaseless babble of the stream. Constant stresses steadiness or persistence and unvarying nature: The constant ticking of the clock lulled him to sleep. Incessant adds to constant the suggestion of annoying repetition: The dog's incessant barking kept him up all night. Perpetual emphasizes both steadiness and duration: One side of the moon is in perpetual darkness. Eternal refers to what is everlasting, especially to what is seemingly without temporal beginning or end: "That freedom can be retained only by the eternal vigilance which has always been its price" (Elmer Davis).
Perennial describes existence that goes on year after year, often with the suggestion of self-renewal: The candidates discussed the perennial problem of urban poverty.