Slytherin was the surname of a pure-blood wizarding family with several notable members, particularly Salazar Slytherin. Salazar was one of the four co-founders of Hogwarts School of Witchcraft and Wizardry and the founder of Slytherin house. He lived in the 10th century.
The Sorting Hat claimed that blood purity was a factor in selecting Slytherins. It was not the main factor, but it suggests that the Sorting Hat took into account the lineage of the student as well as traits. Muggle-born Slytherins existed, but were very rare, as noted insultingly by Scabior the Snatcher.
Professor Salazar Slytherin was a pure-blood wizard of medieval times. He was a Parselmouth (a wizard with the rare ability to speak with snakes) and skilled at Legilimency. He was one of the four founders of Hogwarts School of Witchcraft and Wizardry and the former best friend of Godric Gryffindor, a fellow founder.
Pure-blood was a term referencing wizarding families or individuals descended only from magic, with no Muggles, Squibs or Muggle-born witches or wizards in their family.
The “welcome to Slytherin” letter which Rowling put on Pottermore a couple of years ago says that nowadays there are a lot of Slytherins with “at least” one Muggle parent. That implies that there are now some Muggle-born Slytherins but they are still fairly rare: they don't qualify as “a lot of” on their own.
It is not impossible if a muggleborn witch/wizard have the traits and values of Sytherin, and Slytherin doesn't mean they only accept purebloods but also halfbloods and that halfbloods are really talented and great like Snape he is a potion master and Umbridge also she was a Slytherin.
Although Salazar Slytherin wanted his house to only be made up of wizards of with purest blood, throughout the years they changed it so that anyone can be in Slytherin regardless of their blood status. Not allowing half bloods and muggle horns into Slytherin would basically be racist.
Draco Lucius Malfoy (b. 5 June 1980) was a British pure-blood wizard and the only son of Lucius and Narcissa Malfoy (née Black). The son of a Death Eater, Draco was raised to strongly believe in the importance of blood purity. He looked down on half-bloods and Muggle-borns.
The pure-blood wizards and witches featured in the Harry Potter books are almost all supremacists, while there are some of them who do not advocate ancestral superiority; the Potters, Weasleys, and Longbottoms are old pure-blood families, but no known members of these families are sympathetic to supremacist aims.
An interesting fact of note is that despite the ideals that pure-bloods are inherently more powerful wizards, some of the most powerful or particularly adept wizards and witches in the series are in fact either half-blood (such as Lord Voldemort, Albus Dumbledore, Minerva McGonagall, Severus Snape and Harry Potter) or ...
The Malfoys were a pure-blood wizarding family who were one of the Sacred Twenty-Eight - a list of pure-blood wizarding families published in the 1930s. Known for being aligned with the Dark Arts, the Malfoys had a history with Voldemort, with Lucius Malfoy being a Death Eater in You-Know-Who's innermost circle.
yeh don' have ter be pureblood ter do it." implying that Cedric is a pure-blood. Since Cedric's parents were both wizards, he could not have been a Muggle-born anyway.
Her real parents were Daneel and Dean Novak, Pureblooded wizards. Turns out Daneel was Tom Riddles younger sister, Daneel Riddle. Of course, the Riddles were related to Salzar Slytherin himself, and this made Hermione the living heir of Slytherin.
Harry is a half-blood because his mother was born to a Muggle family while his father was born to a Wizarding couple. It doesn't matter what social standing someone manages to achieve or inherit to those who made the definition. Tonks is a halfblood despite being descended from the Black family on her mother's side.
Luna Lovegood is a Pureblood witch, who was sorted into Gryffindor House during Harry Potter's second year at Hogwarts School of Witchcraft & Wizardry.
Ancient and powerful, the House of Black was the largest and oldest pureblood family in Britain. Its motto, Toujours Pur, or "Always Pure," expressed its members' fanaticism for blood purity, which had led them to marry their cousins for several centuries to avoid "tainting" the family's legacy.
They decided that they needed to see what I looked like with white hair. It meant the first of many bleaching that would become a staple in my life for the next ten years. It took longer than expected to establish my first Malfoy hairdo. You can't just go from one color to another, especially when going lighter.
J.K. Rowling says Draco doesn't have a patronus because he never learned the spell but I think it's because he doesn't have any powerful happy memories to use.
Yes. His mother was the giantess Fridwulfa, who was a member of the giant colony that he and Madame Maxime visited in OotP. His dad was a half-blood wizard, and that makes Hagrid a half-blood.
Yes, although we haven't met any in the seven Harry Potter novels. The Pottermore introduction to Slytherin says: […] we have traditionally tended to take students who come from long lines of witches and wizards, but nowadays you'll find plenty of people in Slytherin house who have at least one Muggle parent.
Joining Slytherin won't affect the story in any notable way (if you truly want to dabble in the Dark Arts, being sorted to this house isn't a prerequisite). However, you may have more chances to talk and get to know your fellow 5th year Slytherin students, including Ominis Gaunt, Imelda Reyes, and Sebastian Sallow.
According to J. K. Rowling, a Muggle-born can become a Death Eater in the rarest of rare circumstances. Although Muggle-borns are descended from Squibs, there is not a single known case of a Squib having children.
