"Apse" is a common architectural term that refers to the semicircular or polygonal end of a building. The spelling of its past tense form, "apsed," is derived from the regular verb form "to apse," meaning to add or build an apse. Its pronunciation is /æpst/ with an "a" sound as in "cat," a "p" sound followed by an "s" sound, and a final "t" sound. The spelling and pronunciation of "apsed" follow the general rules of English verb conjugation.