A hiccup makes a quick "hic" sound. Most people get hiccups sometimes, and they go away by themselves in a few minutes. Your diaphragm is a muscle under your lungs that helps you breathe. In a hiccup it jerks, or spasms, and you cannot stop it. The jerk makes air rush in fast, and then the vocal cords snap shut, which makes the "hic" sound. The glottis is the gap between the vocal cords, and hiccups are a reflex: the diaphragm contracts suddenly, which causes a sudden intake of breath that is cut off when the glottis closes.

A sneeze is a sudden burst of air that rushes out of your nose and mouth. A sneeze is a reflex, which means your body does it on its own: you cannot decide when it happens. A sneeze starts when something irritates the lining of the nose or throat, and sensory nerves send the alarm. A sneeze is a team effort: nerves in the nose send a message to the brainstem, and many muscles then work together to push the air out. A sneeze helps clear dust and dirt out of your nose.

A yawn is a deep breath in with the mouth wide open, often with the eyes closing and a stretch of the body. A yawn lasts about four to seven seconds. People tend to yawn most when they have just woken up or when they are tired, and people often yawn when they are bored. Babies yawn before they are born, and other animals yawn too, including cats, dogs, birds and fish. Yawns are catching: when you see someone yawn, you often yawn too.

People try many home tricks for hiccups, such as holding their breath, sipping ice-cold water or swallowing a little sugar. These are things people try, not proven cures. The NHS says there is no evidence that home hiccup tricks work for everyone, though many people find them helpful, and a science article for children reports a big study that found none of them actually work. Nobody knows for sure why we hiccup, and hiccups have no obvious purpose. Nobody knows for certain why we yawn, either.

Words to know

• diaphragm: breathing muscle
• reflex: automatic body action
• glottis: throat gap
• spasms: sudden muscle jerks
• brainstem: brain base