The term "thirtieth" refers to the ordinal number that represents the position of something in a sequence, specifically the number 30. It is commonly used to indicate the 30th item in a list or the 30th day of a month. In mathematics, it can also denote one part of thirty equal parts, such as in fractions. In the context of time, "thirtieth" can refer to significant events that occur on the 30th day of a month, such as anniversaries or deadlines. For example, April 30 is the thirtieth day of April, often associated with various cultural or historical observances.