What’s the deal with erections, ejaculation, and wet dreams?

What’s an erection? Why does it happen?

Boner. Wood. Stiffy. Hard-on. There are lots of nicknames for erections. An erection is when blood flows into your penis faster than it flows out, and makes the spongy tissue in your penis swell.

When you have an erection, your penis gets bigger and harder. It may stick straight out, or curve up or down. Erections can happen at any point in your life (even when you’re a baby). But you start getting erections more often during puberty.

Erections usually happen when you’re sexually excited (AKA horny or turned on). But during puberty, it’s common to get random erections that happen for no reason at all, like when you’re in math class or doing something else totally non-sexual. This is called a spontaneous erection — it’s an erection you get when you're not sexually turned-on. Spontaneous erections can feel embarrassing, but they go away if you ignore them. As you get older, you won’t have these kinds of erections as much.

It’s common to get erections during the night when you’re sleeping and when you first wake up — that’s where the term “morning wood” comes from.

After you ejaculate (cum), an erection goes away and your penis will get soft again. Some people masturbate when they have an erection. But an erection will also go away after a few minutes if you just wait it out.

What’s ejaculation?

When your penis is hard and you get very sexually excited (turned on), a sticky liquid may shoot out of your penis — this is called ejaculation. Some slang terms for ejaculation include: cum or come, jizz, and shooting your load. Most of the time, ejaculation happens during an orgasm (a sexual release that feels really good). But it's possible to have an orgasm without ejaculating. And it's also possible to ejaculate without having an orgasm.

The liquid that comes out of your penis during ejaculation is called semen, ejaculate, or cum.  It's not the same thing as urine (pee). You can’t pee and ejaculate at the same time — your body blocks pee from coming out when you’re close to ejaculating. (That’s why it can be hard to pee if you have an erection.)

Semen (cum) has sperm in it. When sperm gets inside a vagina, it can cause pregnancy. So if you’re having penis-in-vagina sex, it’s important to use birth control, like condoms. Read more about how pregnancy happens.

Sometimes a thin, slippery liquid drips out of your penis when it’s hard BEFORE ejaculation — this is called pre-ejaculate or precum. Precum is totally normal. Precum may have a tiny bit of sperm in it, so it can cause pregnancy — but this is rare.

What’s a wet dream?

You might wake up in the morning with sticky underwear or sheets and realize that you ejaculated in your sleep. This is called a wet dream, and it's totally normal — especially during puberty. Sometimes when you sleep, your penis gets hard and you ejaculate. Maybe you had a sexy dream, or maybe your penis was stimulated when it rubbed against your sheets.

Wet dreams are common. As you get older, they happen less often or go away altogether.