l2

L2 is an abbreviation used in diverse domains to denote different concepts, often signaling a second item or a squared quantity depending on context. This article surveys several common meanings in linguistics, computing, mathematics, and immigration.

In linguistics and language education, L2 refers to a learner's second language—the language learned in addition to one's native language (L1). The study of L2 acquisition, proficiency, and pedagogy investigates how people learn and use a language beyond their first tongue, including factors such as age, exposure, and instruction.

In computing and computer architecture, L2 commonly denotes Level 2 cache, a small, fast memory located between the CPU core and main memory. An L2 cache stores frequently accessed data to reduce access times and improve overall system performance. It is typically larger and slower than L1 cache but faster than main memory.

In mathematics and data science, L2 denotes the L2 space and related concepts. The L2 space consists of square-integrable functions, with the L2 norm defined as the square root of the integral of the square of a function. The L2 distance (or Euclidean distance in finite dimensions) is derived from this norm and is widely used in statistics, signal processing, and machine learning. L2 regularization, also known as ridge regression, adds a penalty equal to the squared magnitude of model parameters to prevent overfitting.

In immigration law, the L-2 visa (often written L2) designates dependent visa status for spouses and children of L-1 visa holders, allowing them to accompany the primary worker or nonimmigrant.