We just learned about Waves and Wavelength.
Frequency means the number of times that something happens during a certain length of time.
So for example, if you clap your hands 3 times,
then 3 is the number of times
If you count out 10 seconds,
that is the length of time.
If you clap your hands 3 times while you count out 10 seconds,
then 3 over 10 is the frequency.
You can write it like 3/10.
If you clap your hands 7 times in that 10 seconds, that's 7/10, which is a higher frequency
If you clap your hands just 1 time in that 10 seconds, that's 1/10, which is a lower frequency
We can use frequency to measure lots of things from music to heart beats to airplanes!
(from: wikipedia - frequency)
Sometimes we also use the word occurrences instead of saying number of times.