Answer:
The frequency and period of a wave have an inverse/opposite relation. This means as one value goes up, the other one goes down.
Explanation:
Frequency means how often a wave occurs.
Period means how long it takes for one wave to occur.
If a wave takes a longer time to occur, then the wave cannot occur faster.
Think of a wave represented by a playground swing set. If you swing higher (high period), you have a greater period. But, you can't swing 'faster' back and forth (low frequency).
If you don't swing as high (low period), you can go back and forth faster (high frequency).
