The prefix "temporary" before a rank (e.g. temporary detective sergeant, abbreviated T/DS) denotes an officer who has been temporarily promoted to a rank (and so who does actually hold that rank, albeit on a temporary basis), whilst the prefix "acting" (e.g. acting inspector, abbreviated A/Insp) denotes an officer who is performing the role of a higher rank than the one actually held (sometimes informally termed "acting up"). Temporary ranks are often used for set periods (e.g. a six-month appointment to a particular role), whereas acting ranks, although sometimes held for extended periods, are often used for a very short time (e.g. a single shift when additional supervisory officers are required, or to replace an officer on short-term leave).