Essentially any delay or lapse in time. In general, it is the time between initiating a request in the computer and receiving the answer. Data latency may refer to the time between a query and the results arriving at the screen or the time between initiating a transaction that modifies one or more databases and its completion.
Disk latency is the time it takes for the selected sector to be positioned under the read/write head. Channel latency is the time it takes for a computer channel to become unoccupied in order to transfer data. Network latency is the delay introduced when a packet is momentarily stored, analyzed and then forwarded.
With malicious software, latency is the period between infection and the first obvious damage to the host system. Many viruses or logic bombs written by amateurs have a short latency and are therefore relatively easy to detect; however, more vicious malware can lie dormant or replicate to many other hosts and then wreak havoc unexpectedly. See logic bomb