What does log mean?
Log is a compact, polysemous English noun and verb whose meanings range from the practical to the technical. As a noun, it commonly means a cut section of a tree trunk, especially one ready for use as timber or fuel, and it also means a written record kept over time. In computing, a log is a structured file or stream that records events, transactions, or system activity; this sense has become especially familiar through software, servers, and online services. In mathematics, log denotes a logarithm, the exponent to which a base must be raised to produce a given number. As a verb, log means to enter information in a record, to cut trees into logs, or, in phrases such as log in and log out, to enter or leave a computer system. The word also has a maritime history: sailors used a log line to check a ship’s speed, helping give rise to the unit knot.
As a noun, log denotes a cut section of a tree trunk; a written or electronic record; a mathematical logarithm; or a nautical device formerly used to measure a ship’s speed.
"A pile of freshly cut logs lay beside the sawmill."
The computing sense is usually a structured record of events or activity, while the mathematical sense generally denotes a logarithm to base ten unless another base is specified.
As a verb, log means to record information, to cut trees into logs, or to enter or leave a computer system. It can also mean to record a measured distance, speed, or achievement.
"Users must log in before they can change their settings."
The standard plural is logs. In computing, logs usually refers to files or collections of recorded events rather than pieces of timber.
"The server wrote the failed login attempts to its logs."
Before GPS, sailors measured a ship’s speed with a knotted log line—the ancestor of the unit we still call a knot.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does log come from?
The tree-trunk sense comes through Middle English logge, probably from Old Norse lǫggur, meaning a tree trunk. The record and computing senses developed in association with the maritime log and the log line used to measure a ship’s speed and distance, while the recording verb developed from the noun. Mathematical log is short for logarithm, from Latin logarithmus and Greek logos, meaning ratio; that Greek root also underlies logic, dialogue, and monologue.
Related word forms
How log is actually used
The computing verb phrases are written as two words: log in and log out. The noun log can sound traditional or institutional when it means a diary or official record, while the expression keep a log is broadly idiomatic. In general American speech, log may be pronounced with either the open vowel of law or the vowel of cot.
Easily confused with log
A lag is a delay or a falling behind, whereas a log may be a piece of wood, a record, or the act of recording information.