Septua- is a Latin root that refers to the number seven. It is commonly used to indicate seven-fold or seventh in words such as septuagenarian or septennial. However, there are several synonyms for this root that can be used in different contexts. For instance, hept- is a Greek-derived prefix that is also used to indicate seven, as seen in words like heptathlon or heptagon. Additionally, septimal is an adjective that describes a system or measurement based on the number seven. Other terms like septenary, septiform, and septuple can also be used to signify the number seven or something that occurs in sevenfold or seven parts.