Note 1: This is NOT a list of character skills, just a list of xianxia terms in Grandmaster of Demonic Cultivation (GDC) aka Mo Dao Zu Shi (MDZS) that are likely to come up in tags, so I might as well give a brief explanation of them.
Note 2: This is by no means a full list of what goes on in canon, just a primer I slapped together from reading the GDC book-- the novels published by Seven Seas have glossaries at the back-- and other xianxia novels and comics, and a bit of extra research to fill in some gaps. There are people who have done even deeper dives into the genre, like whoever runs the Immortal Mountain site. If I made a mistake somewhere or the official translations contradict anything I've already written, I'll make the necessary edits.
Note 3: I'm a Southeast Asian of Chinese descent living in a Southeast Asian country with close historical and cultural ties to China. Some of the Chinese culture prevalent in this region has changed over time and distance, but the roots are still the same, so I try to write what knowledge I do have in ways I understand them to make them more accessible.
People who study under the same teacher or master or are raised in the same sect are called martial siblings. Literally, the titles they call each other and their teacher stems from the hanzi for "teacher/master", with a familial term slapped on the end to denote their relationship to each other using their master as a baseline. For example, one's master is "shifu" or literally "master father", and an older male student under the same master is "shixiong" or "master elder brother", typically translated as "senior martial brother" or just "senior brother". There are also martial uncles and aunts, especially if the master's master took in multiple students. These terms can also extend to the blood family of the master to show respect, though the blood family of the student don't usually get this sort of treatment.
Despite the terminology, the sect is not considered the same as blood or adopted family. The master doesn't actually adopt a student as their child nor gives them their family name-- this would be considered rude towards the student's biological family (and if the master really wanted a student as part of their family, they'd get said student to marry one of their biological children). Instead, this system shows the hierarchy, which keeps the sect organized and gives people something to call their fellow sect members by as a sign of respect, especially towards elders-- calling someone older by just their birth name is considered disrespectful, even if the age difference is minimal.
martial siblings
Despite the terminology, the sect is not considered the same as blood or adopted family. The master doesn't actually adopt a student as their child nor gives them their family name-- this would be considered rude towards the student's biological family (and if the master really wanted a student as part of their family, they'd get said student to marry one of their biological children). Instead, this system shows the hierarchy, which keeps the sect organized and gives people something to call their fellow sect members by as a sign of respect, especially towards elders-- calling someone older by just their birth name is considered disrespectful, even if the age difference is minimal.