In Roman law, status describes a person's legal status. The individual could be a Roman citizen (status civitatis), unlike foreigners; or he could be free (status libertatis), unlike slaves; or he could have a certain position in a Roman family (status familiae) either as head of the family (pater familias), or as a lower member (filii familias).
In the Roman state, according to Roman civil law (ius civile), only Roman citizens had the full civil and political rights. In regard to status civitatis, in the Roman state, there were cives, Latini and peregrini, and foreigners. Outside the Roman state, there were externi, barbari and hostes.
Status familiae is the legal status of an individual in the family. The pater familias had the authority in the family (patria potestas), and everyone was subjected to him based on adgnatio (kinship only from father's side). This had an impact in private law. There is a distinction between alieni iuris (persons under patria potestas) and sui iuris (persons autonomous of patria potestas, who could only be the pater familias himself). Filius familias had ius suffragii and ius honorum, but in the area of private law he was restricted because of patria potestas.
The social and legal status of slaves in the Roman state was different in different epochs. In the time of old civil law (ius civile Quiritium) slavery had a patriarchal shape (a slave did the same job and lived under the same conditions as his master and family). After Rome's victorious wars, from the 3rd century BC, huge numbers of slaves came to Rome, and that resulted in slave trade and increased exploitation of slaves. From that time on, a slave became only a thing (res)- servi pro nullis habentur.
The legal state of slaves was based on the fact that the slave was not a subject but an object of law. A master had the right of ownership over the slave. He could sell him, give him in pawn but certainly could not harm or kill him. If someone injured his slave, a master could initiate legal proceedings and demand protection. The ownership over the slave was called dominica potestas, and not dominium like the ownership of objects and animals.