Old MACDONALD had a farm E-I-E-I-O And on his farm he had a cow E-I-E-I-O With a moo moo here And a moo moo there Here a moo, there a moo Everywhere a moo moo.
In the example Old McDonald had a farm, The noise the animals make is the onomatopoeia in the song. Like the cow going MOO is the onomatopoeia in this song.
In the example the wheels on the bus, the onomatopoeia is the noises the bus is making while it's driving. Like the wind shield wipers going SWISH is the example of onomatopoeia.
So onomatopoeia is basically a noise that some or something is making. 💥 So for another example is a car starting when it makes that CLICKING noise and the "vroom vroom" noise.