July 21, 2025
What’s the difference between sperm and semen?
And can pre-ejaculate get you pregnant?
Semen, sperm, spunk, cum, ejaculate, pre-cum, seminal fluid. These are just some of the many words we use to describe what comes out of an erect penis.
Some of these terms can be used interchangeably, but they’re not all the same. Do you know the difference?
What is sperm?
Sperm are . The word “sperm” can refer to spermatozoon (singular) or spermatozoa (plural).
Sperm are tiny cells with an oval-shaped body and a long tail. They measure just of a millimetre in length and can only be seen with a microscope.
Sperm are produced in the two (testicles). The testes are glands located inside the scrotum (the skin sac underneath where the penis is attached to the body).
The testes begin producing sperm at puberty. Sperm production then continues , beginning to decline around . The testes 200 million sperm every day.
To develop, sperm of 34–35°C, which is lower than core body temperature (usually ). This is why the testes are located in the cooler scrotum and not in the abdomen or pelvis.
Each sperm carries , which are made up of DNA and genes. When a sperm cell fertilises a female reproductive cell (an ovum or egg), the genetic information of the sperm and ovum combines to form an embryo.
What is semen?
Ejaculated sperm has to reach the uterine () tubes to fertilise an egg. This is a long journey, so sperm are carried in a fluid that nourishes and protects it (seminal fluid).
Semen is the mix of sperm and seminal fluid together. It is Latin for “seed” , “to sow”. Semen only exists outside the body, because sperm and seminal fluid only combine at the point of ejaculation.
Seminal fluid is the sex glands. These are the seminal vesicles and prostate, which sit just behind and below the bladder, respectively.
The produce a thick, gel-like substance. It clumps the sperm together immediately after ejaculation and provides the sperm with energy (fructose) to survive their journey.
This fluid is alkaline – the opposite to acidic – which protects sperm in the vagina.
The prostate secretes a with acids that the semen. This helps the sperm to separate from the initial clump so they can travel through the cervix and uterus to the uterine tubes.
The prostate also provides , which is essential for sperm survival.
Ejaculating into the urethra, the narrow tube that runs through the penis and also transports urine. At this point, they combine as semen.
Semen 10% sperm and 90% fluid from the seminal vesicles and prostate.
What happens after ejaculation
usually produces between 1.5 and 5 millilitres of semen, and each mL contains anywhere between .
If semen is ejaculated into a vagina, sperm have to travel to reach the uterine tubes, which is the for fertilisation.
The fastest and healthiest sperm travel this distance – about 3,000 times their body length – in .
For a human of average height, this equates to swimming about 5 kilometres in half an hour. That means sperm can swim twice as fast as the current for a 5km open water swim.
Does ‘pre-cum’ have sperm in it?
An aroused and erect penis can secrete up to 4mL of pre-ejaculate (pre-cum), which is completely different to semen.
Pre-ejaculate is produced by different sex glands – the small that sit just under the prostate. It is a mucus fluid that lubricates and flushes out the urethra in the penis.
Theoretically, pre-ejaculate doesn’t contain sperm. However, one small found the pre-ejaculate of about 40% of men they studied contained sperm, though in very low numbers.
The risk of getting pregnant from pre-ejaculate is .
What can semen say about your overall health?
Semen is usually creamy-white or pale grey. It often has a faint ammonia or bleach smell, because of its .
However its colour, consistency and smell and even on different days for the same person.
If semen has a foul odour, it and should be checked by a doctor.
Contraception and fertility
A is a form of male contraceptive. This involves cutting – the tubes that carry sperm from the testes to the urethra. After a vasectomy, ejaculating will produce slightly less semen and it won’t contain sperm.
have also started for a new potential that blocks sperm production in the testes.
– of too many damaging chemicals and not enough antioxidants – has a negative impact on sperm health and strongly .
The has published a range of values for semen volume and sperm number, concentration, movement and structure among fertile males. However, low sperm count does not always mean lower fertility.
To , it’s recommended to eat a healthy diet rich in antioxidants, exercise regularly, maintain a healthy weight, and not smoke, use recreational drugs or drink a lot of alcohol.
, Associate Professor of Medical Sciences,
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