O am not sure I understand your question

O am not sure I understand your question.

However, it is a good opportunity to stress the importance of language, symbols and, generally, of precision in Science.

I understand your question to be : What is Period in Physics ? You might have notice that I spelled Period with capital "P" as I would Time when using the word in a scientific context.

Period s a word of many meanings. To give you just one, a period in Geology (and geology is a science) is the Holocene.

Now, if I understood you correctly, the Period of a wave (that is elastic or electromagnetic waves) is the inverse of frequency or, if you prefer, the wavelength divided by the velocity.