Half-blood

The_potters_hp.JPG is the son of a pure-blood wizard and a Muggle-born witch. "Most wizards these days are half-blood anyway. If we hadn’t married Muggles we’d’ve died out."

- Ron Weasley discussing blood purity

Half-blood is the term commonly given to wizards and witches who have both magical and Muggle heritage. As pure-bloods claim to have no Muggle ancestry whatsoever, those who have and acknowledge their Muggle as well as their wizarding heritage would be considered half-bloods. By the 1990s, half-bloods were the most common type of magical person, as the wizarding population would become extinct without inter-marriage with Muggles and Muggle-borns.

Due to the dominance of the magic gene, children born to at least one magical parent will always be magical themselves, meaning that a non-magical child born to a Muggle and a wizard is a Squib, not a Muggle.

Attitude Towards Half-Bloods
"You dare speak his name? YOU FILTHY HALF-BLOOD!"

- Bellatrix Lestrange to Harry Potter after he uses the name Voldemort

Those who believe in the importance of blood purity consider half-bloods inferior for their Muggle heritage, though not as bad as Muggle-borns. They often use the term "half-blood" in a derogatory manner, similar to the epithet "Mudblood"; Bellatrix Lestrange and the portrait of Walburga Black did so on multiple occasions.

Some half-bloods express prejudice towards those with Muggle heritage, despite having some themselves, and cling to what wizarding heritage they have. Notably, Lord Voldemort hated Muggles and Muggle-borns, despite having a Muggle father. Severus Snape may be another example; his self-entitled nickname was "Half-Blood Prince" because his mother, Eileen Prince, was a pure-blood witch and his father, Tobias Snape, was a Muggle. However, Remus Lupin reported that he never used the nickname openly. This, as well as Snape's membership in the Death Eaters, suggests he may have been ashamed of his Muggle heritage, at least in his early life. In fact, these people, along with some other Death Eaters, pretend to be pure-bloods, hiding their Muggle heritage from anyone else.

When the Ministry of Magic fell under Voldemort's control in 1997, Muggle-borns were openly persecuted and pure-bloods were favored. Half-bloods were still accepted at Hogwarts School of Witchcraft and Wizardry, but were not treated as well as the pure-blood students.

Pure- or Half-Blood Parent & Muggle Parent

 * Seamus Finnigan — pure- or half-blood mother, Muggle father
 * Mafalda — pure-blood or Squib father, Muggle mother
 * Tom Marvolo Riddle/Lord Voldemort — pure-blood mother, Muggle father
 * Severus Snape — pure-blood mother, Muggle father
 * Dean Thomas — pure- or half-blood father, Muggle mother
 * Bowman Wright — pure- or half-blood mother, Muggle father

Pure- or Half-Blood Parent & Muggle-Born Parent

 * Alfred Cattermole — pure- or half-blood father, Muggle-born mother
 * Ellie Cattermole — pure- or half-blood father, Muggle-born mother
 * Maisie Cattermole — pure- or half-blood father, Muggle-born mother
 * Aberforth Dumbledore — pure- or half-blood father, Muggle-born mother
 * Albus Dumbledore — pure- or half-blood father, Muggle-born mother
 * Ariana Dumbledore — pure- or half-blood father, Muggle-born mother
 * Harry Potter — pure-blood father, Muggle-born mother
 * Nymphadora Tonks — pure-blood mother, Muggle-born father
 * Hugo Weasley — pure-blood father, Muggle-born mother
 * Rose Weasley — pure-blood father, Muggle-born mother

Half-Blood Parent & Half-Blood Parent

 * Teddy Lupin — half-blood father, half-blood mother

Two Magical Parents, Known Muggle Ancestry

 * Albus Severus Potter — half-blood father, pure-blood mother
 * James Sirius Potter — half-blood father, pure-blood mother
 * Lily Luna Potter — half-blood father, pure-blood mother

Unknown Combination of Parental Status

 * Hannah Abbott — at least one known Muggle ancestor
 * Susan Bones — at least one known Muggle grandparent
 * Millicent Bulstrode — at least one known Muggle ancestor
 * Mundungus Fletcher — at least one known Muggle ancestor
 * Remus Lupin — at least one known Muggle ancestor

Behind the scenes

 * On J. K. Rowling's draft list of students in Harry Potter's class, which is not considered canon due to several contradictions with the novels, the following students were mentioned as half-bloods :
 * Susan Bones
 * Mandy Brocklehurst
 * Millicent Bulstrode
 * Michael Corner
 * Tracey Davis
 * Anthony Goldstein
 * Wayne Hopkins
 * Megan Jones
 * Su Li
 * On the draft class list, Hannah Abbott was listed as a Muggle-born, but in a later interview, Rowling stated that she had always thought of Hannah as a pure-blood. To compromise, she was made a half-blood.

Notes and references
Sang-Mêlé