A defendant is any party who is required to answer the complaint of a plaintiff in a civil lawsuit before a court, or any party who has been formally charged or accused of violating a criminal statute.

A defendant in a civil action usually makes his or her first court appearance voluntarily in response to a summons, whereas a defendant in a criminal case is usually taken into custody by a peace officer and brought before a court, pursuant to an arrest warrant. The actions of a defendant, and its counsel, is known as the defence.

A respondent is the parallel term used in a proceeding which is commenced by petition.

Historically, a defendant in a civil action could also be taken into custody pursuant to a writ of capias ad respondendum and forced to post bail before being released from custody. However, a modern day defendant in a civil action is usually able to avoid most (if not all) court appearances if he or she is represented by a lawyer whereas a defendant in a criminal case (particularly a felony or indictment) is usually obliged to post bail before being released from custody and must be present at every stage thereafter of the proceedings against him or her.

In an informal usage and non-legalistic sense outside the legal context, the term respondent can be used to refute or response to a thesis or an argument in question [[1]].

In cross-cultural communication , a respondent is the second person responding to the meaning or message from an original source which has been contextualised [[2]] or decoded for the understanding of respondents as recipients or hearers of the message occurring from a different cultural context.