Half Blood is a term for a witch or wizard that has 1 magic parent and 1 Muggle parent. Most of the wizarding world is either made up of half bloods or muggle-borns. There is no derogatory term for half bloods like there is one for muggle-borns (mudbloods). So the purebloods that think they are better than everyone else, can't call them a bad name.
Seamus: im half-and-half. dad's a muggle. mum's a witch.
Dean: yeah im half blood
. my mum's a muggle and my dad's a wizard.
Someone who is 100% of a certain nationality. Someone could be a Greek pureblood, Bulgarian pureblood, Russian pureblood, Mexican pureblood, etc.
Sofia: Yeah me and the rest of my family are Greek purebloods.
Nina: No way! Im a Bulgarian pureblood!
Vlad: Im a Russian pureblood!
Steve: Well this is awkward....im not a pureblood