In law, when someone is said to be acting in a position it can mean one of three things.

• The position has not been formally created yet
• The person is only occupying the position temporarily, to ensure continutity
• The person does not have a mandate

The term "acting" is often used in one of these senses to refer to a temporary occupant of an office in government. An "acting" official holds office to ensure both the stability and continuity of his department will continue despite the absence of a formal leader.

For example, if the United States Secretary of State died suddenly in office, the United States Deputy Secretary of State would take over. However, he would only be "acting" in the position, as he will not formally hold the office until he is confirmed by the United States Senate, as required by the constitution.

Similarly, in present-day Iraq, where there is no constitution, all the ministers of the government are said to be "acting." For example, the "Acting Minister of Finance" may run Iraq's financial policy until a more formal department of finance can be created. Once a new constitution is created, and these offices are legally established, the ministers will cease to be "acting."

Acting officials almost always do very little while in office, as it is usually considered improper for someone to exercise full authority when they have inherited their office by accident, as opposed to being specifically hired or elected to it.

Acting for has the same basic meaning as "acting", except it indicates that the original occupant of the position still formally holds power.

For example, occasionally when Francisco Franco was too ill to exercise his powers, his deputy, Prince Juan Carlos was said to be "acting for" Franco. Franco was still formally the nation's leader, as he had not died or resigned, but Juan Carlos was executing the powers of the office.

See also: Acting President, Acting governor