"Eighth" Natural Recordings by Native Speakers
The word "eighth" is an adjective or adverb that refers to the number 8 or a place, position, or time that is eight in a series or sequence. It can be used to describe something that comes after the seventh item or event and before the ninth. For example:
"The eighth team to qualify for the tournament is France."
"The eighth grade students went on a field trip to the museum."
Eighteen is a number that comes after seventeen and before nineteen. It is the age of majority in some countries, indicating that a person is considered an adult and has full legal rights and responsibilities. It can also refer to a period of time, such as the late teens, or used as a quantity, as in "eighteen people came to the party".