There are numerous words that you can use as synonyms to the term "ten days." These include such words as "decade," which refers to a period of 10 years, "week and a half," "two assemblages," "ten solar days," and "ten-day spell." All of these can be utilized in various situations where you want to express the idea of a duration of ten days, with slightly different nuances in meaning between them. It is always useful to have a variety of synonyms for any word in your vocabulary, as it allows you to express yourself in different ways and avoid repetition.