The term "ninetieth" refers to the ordinal number that represents the position of something in a sequence, specifically the number 90. It is commonly used to indicate the rank or order of an item, person, or event, such as in a race or a list. For example, if someone finishes in the ninetieth place in a marathon, they are the 90th runner to cross the finish line. In mathematics, "ninetieth" can also relate to fractions, where it represents one part of a whole divided into ninety equal parts. This is often expressed as 1/90. Additionally, in the context of time, a ninetieth anniversary marks 90 years since a significant event, such as the founding of an organization or the birth of a notable individual.