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"I don't let my stammer hold me back or stop me from achieving" - that's what Jack has said about his stammer.

Jack was talking to Newsround as part of International Stammering Awareness Day - a day to raise awareness about stammering.

He had three bits of advice he'd give when talking to someone with a stammer:

Stammering affects the way people speak.

People who have a stammer often find it hard to get across what they want to say. They sometimes get stuck trying to say certain words, or are not able to say them at all.

It's more common in boys than girls, and studies suggest around one in 20 children under the age of 12 will have a stammer at some point.

Around four in five children who stammer will grow out of it - but it's difficult to predict when that'll happen.

Dylan has had a stammer since he was six years old.

But he hasn't let it stop him from being the voice of a national stammer awareness campaign.