Decagonal is a shape that has ten sides and ten angles. If you are looking for synonyms of this term, there are a number of words that could be used. One of the most common is "decagon", which is simply an alternate term for the same shape. Another option might be "ten-sided", which is a more descriptive way of referring to the shape. Other possibilities might include "decapentagon", which refers to a ten-sided polygon with each of its angles measuring 144 degrees, or "decagonon", which is another term for a ten-sided polygon. Whatever word you choose, it is important to be clear and specific in your language to avoid confusion.