LTR

LTR is an initialism that can refer to several concepts across different fields. This article outlines the major uses in science and everyday language.

Long terminal repeat

In genetics and virology, a long terminal repeat is a repetitive DNA sequence found at the ends of retroviral genomes and many retrotransposons. LTRs contain regulatory elements such as promoters and enhancers that control transcription, as well as signals for transcription initiation and termination. They can influence the expression of adjacent genes and contribute to genome structure and evolution. LTRs are also used in molecular biology and gene therapy vector design due to their regulatory capabilities.

Left-to-right

Left-to-right denotes the direction in which text is written and read in many scripts, including English, Spanish, French, and other Latin-based languages, as well as several non-Latin scripts presented horizontally. In computing and typography, LTR affects layout, rendering, and bidirectional text handling, especially when combined with right-to-left scripts in multilingual content.

Learning to Rank

Learning to Rank is a class of machine learning methods that aim to optimize the ranking of items (such as web pages or products) by relevance to a query. It is widely used in search engines and recommender systems. Models are trained to optimize ranking-oriented metrics (e.g., NDCG, MAP) and can be pointwise, pairwise, or listwise. Techniques range from traditional algorithms like RankNet and LambdaRank to modern neural architectures.

Long-term relationship

In social and relationship contexts, a long-term relationship refers to a romantic partnership expected to endure for an extended period. The term emphasizes ongoing commitment and shared life plans rather than brief or casual dating. The definition of “long-term” varies among individuals and cultures.