Use interminable to describe something that has or seems to have no end. Your math class. Your sister's violin recital. A babysitting job where five kids are going through your purse and the parents didn't leave a number.
Something that is interminable is often boring, annoying, or hard to bear, such as an interminable noise. A near synonym is incessant, which also refers to something unpleasant that continues without stopping. It descends from the Latin prefix in- "not," terminare "to end," and the suffix -abilis "able to." Latin terminare is also the source of the English verb terminate "to end" and the corresponding noun termination "an act of ending something."