Saiyan

The Saiyans were one of two races who lived on Planet Vegita. The other race was the Tsufuru. As the Saiyans were stronger than the Tsufuru, the Saiyans destroyed all of the Tsufuru. One thing that sets the Saiyans apart is their tail. If they look at the light from a full moon they can turn into Oozaru, a giant ape. In this form they are 10 times stronger than normal.
After conquering the planet the Saiyans were hired by an alien named Frieza. The Saiyans' mission was to conquer worlds and then sell them to the highest bidder. However, Frieza became worried about the Saiyans' power and destroyed planet Vegita. The only Saiyans left were Goku, Vegita, Brolli, Nappa, Raditsu, Paragus, and Taurus. During the course of DragonBall Z, the only true Saiyans remaining are Vegita and Goku.
The Saiyans are a warrior race and as such have incredible fighting abilities. As they fight their skills increase but unlike most races the Saiyans get stronger after recovering from a severe battle. After a certain point the Saiyans no longer gain greatly in strength. After they reach this plateau they have the ability to reach a new level of power. The Saiyans have the ability to achieve Super Saiyan Stage 1. However there are some conditions to be met. The person must have a pure heart, be strong enough to surpass a normal Saiyan. With these met all that is needed is extreme rage to trigger the transformation. Once transformation is accomplished it is easier to accomplish the next time do the fact that the rage is not needed again. However after achieving Super Saiyan Stage 1, the Saiyan is capable of attaining even more strength. There are a total of five levels. There is Super Saiyan Stage 1, Ultra Super Saiyan, Super Saiyan Stage 2, Super Saiyan Stage 3, and Super Saiyan Stage 4. Of the two remaining true saiyans Goku reaches all the levels and Vegita reaches SSJ1, USSJ, SSJ2, and SSJ4. Sidenote: If the Saiyans still have their tail they can reach the level of Super Saiyan Oozaru
On the Earth Goku and Vegita marry and have children with Saiyan traits. Goku and his wife have to childern. One is Gohan and the other is Goten. Vegita and his wife have two children, one is named Trunks and the other is Bra.
After Goku and Vegita there are no more true Saiyans and the race lives on in the bloodlines of their children and grandchildren.

While only a few true full-blooded Saiyan (or more properly: Saiyajin) in the "official" Dragonball Z series (namely, Son Goku, Vegeta, Raditz, and Nappa), many others show up in the numerous Dragonball Z movies, including Bardok, Goku's father, in the Bardok TV Special, and as the enemies in several of the movies, including The Tree of Might (AKA "The Mega-Vigorous Battle for Planet Earth"), where the leader of the group trying to destroy the Earth looks exactly like Goku, except his skin is gray (the reason this is so is never explained). Also, there is an enemy who shows up in a couple of the movies named Brolli, who is apparently quite tough (his movies have not been released in the US at the time of this writeup)

The Saiyans were incredible fighters. Not only were they very strong from birth, each time they are heavily injured and then recover, their strength increases dramatically. For some time, they worked for Frieza (whose name means freezer; his brother was named Coola, or cooler), a mysterious and very powerful being who used them as troops to decimate planets, which he would then sell to other races looking for a new home to colonize. But Frieza ended up destroying planet Vegeta because he feared the power of the Super Saiyans, a power which had not been seen in a thousand years. When a Saiyan reaches Super Saiyan, his hair glows yellow, and an aura surrounds their body. They become much faster and stronger. Only a few Saiyans survived the destruction of Vegeta, including Goku. For all the neat things that happen to Frieza on Namek read my writeup in Frieza.

An interesting thing about the Saiyans is that they are all named after vegetables. Vegeta, naturally, just means vegtable (as he is named after the planet that the Saiyans are from). Nappa, his sidekick, is named after cabbage. Raditz, Goku's brother, is a radish. The word bardok, Goku's father's name, refers to a kind of root vegetable native to Japan (you can get it at finer sushi restaurants). And Goku's birth name, Kakarrot, means carrot - he was named Goku (monkey) by an old man who found him after his spaceship crashed on Earth.

     The Saiyans were an ancient race from Planet Vegita. They were accompanied by another race called the Tsufuru. The Saiyans clearly overpowered the Tsufuru, and conquered them. They were often hired out to conquer and/or destroy other planets and races. The Saiyans are a race of born warriors. They are gifted with many abilities, including the ability to use many Ki attacks, and the ability to their power to increase dramatically after serious injuries. This business led to their demise when an alien, Frieza, who later became afraid of their increasing power, hired them. Bardok, father of Goku, leads the Saiyans to revolt against Frieza. Frieza easily destroys them along with the entire planet. The only Saiyans to survive this are Goku, Vegita, Broly, Nappa, Radditz, Paragus, and Taurus. All of these Saiyans were sent away at the time. Goku was sent to away to Earth to grow up to destroy Earth. When he is the age when he is supposed to destroy Earth; Radditz, Nappa, and Vegita arrive. Radditz reveals Goku’s Saiyan name, Kakarot. Throughout the series Radditz and Vegita are the only two to really call him this. Goku and Chichi have two kids, Gohan and Goten, and Gohan and Videl had one child named Pan. Gohan and Goten are half Saiyan and half Human, and Pan is a quarter Saiyan and three quarters Human. Vegita and Bulma have two kids Trunks and Bra who are both half Saiyan and half Human.

     Saiyans are able to obtain certain Saiyan “levels” reguarding their power level, or Ki. The first level and most basic level is Saiyan. From this level they can obtain 2 power levels. First they can transform into Oozaru, or Were-Monkey. This is done when a Saiyan that still has their tail looks at the full moon. Their power is increased by many times, and grows to extreme sizes. The second way they can go is Super Saiyan. Their power level must be a certain amount to get to this amount, plus a rage level needs to be reached. This level is characterized by their intense increase in power, and their new look. Their hair turns from the normal black with black eyes, to a golden blond hair and Blue-green eyes. Goku is the first to reach this level on planet Namek. After fighting Frieza for a while and he uses the Spirit Bomb attack, Frieza kills Krillin and attacks Picollo to the point where he looks dead. This causes Goku to become extremely enraged and allows him to obtain Super Saiyan. Vegita, Gohan, Goten, Trunks, Gotenks, Gogeta, and Broly all obtain this level. After this the Super Saiyan 2 can be reached. Super Saiyan 2 is very similar to the first level. The Saiyan’s hair grows slightly, and the power level is increased. Gohan is the first to obtain this level while he is fighting Cell when Cell crushes Android 16’s head. Goku, Gohan, Vegita, and Broly all obtain this level. After this level is Super Saiyan 3. At this level the hair grow a lot, and the power is increased a lot. You will also notice the Saiyan no longer has eyebrows and the face seems longer. This level is hard to keep because there is a constant loss of energy during this state. Goku is the first to obtain this level during the Majin Buu saga. Gotenks also obtains this level. After this level Oozaru Gold or Golden Were-Monkey can be reached. This level can be reached while looking at the moon in Super Saiyan. It is different from regular Oozaru by the golden fur instead of brown and the increased power level. This level is required to become Super Saiyan 4. Goku and Vegita obtain this level. Super Saiyan 4 is a very different level. This level is not always considered a Super Saiyan level because it does not fit the characteristics. The Saiyan grows in size and is covered in red fur. The hair returns to black along with the eyes, which get a red ring around them. Gogeta is an exception, his hair turns red and his body fur becomes brown. There is an intense power increase, and the tail is required. Goku’s tail was wished back so this could be accomplished to defeat Bebi. Vegita uses Bulma’s invention, the Brute Ray, to reach this level because he lost his tail. Goku, Vegita, and Gogeta obtain this level. Once a level is obtained, it is much easier to rise into it after that.

     Saiyans, along other races, have the ability to fuse. The fusion is done a few ways, and the more known fusions are between Goku and Vegita, and Goten and Trunks.