Eight-day is a term used to describe a period of eight consecutive days. There are several other synonyms for the word eight-day, including a week, which is the most commonly used term. Other synonyms include an octad, an octave, and an eight-day period. An octad is a term used in music to describe an eight-note scale. An octave is an interval between two notes that are eight steps apart. An eight-day period refers to a specific period of time that lasts for eight days. These synonyms for the term eight-day are useful when describing events or activities that take place over a specific period of time.