All articles A–Z

Affine projection algorithm

The affine projection algorithm is an adaptive filtering algorithm, introduced by Ozeki and Umeda in 1984, that converges faster than LMS and is widely used in echo cancellation.

Affine root system

An affine root system is an infinite root system whose quotient is a finite root system, underlying affine Kac–Moody Lie algebras and classified by Macdonald in 1972.

Affine space

An affine space is a set of points on which a vector space acts as translations, so point differences are vectors but points cannot be added or compared to a fixed origin.

Affine subspace

An affine subspace is a subset of a vector space formed by shifting a linear subspace away from the origin; it equals the solution set of a system of linear equations.

An affine transformation is a geometric mapping combining a linear transformation such as rotation, scaling, or shear with a translation, preserving straightness, parallelism, and ratios along parallel lines.

Affine type system

An affine type system is a type system where each value may be used at most once but may be freely dropped, relaxing linear types.

Affine variety

An affine variety is a subset of affine space defined as the common zero set of a collection of polynomials, the basic object of classical algebraic geometry.

Affine variety of parallelism

The affine variety of parallelism is the parallelism structure of affine geometry, splitting lines into parallel classes, one per direction; adding a point at infinity for each class yields a projective plane.

Affinity (software)

Affinity is a suite of graphic design, photo editing, and page layout applications developed by Serif, acquired by Canva in 2024, and relaunched in 2025 as a free app.

Affinity analysis

Affinity analysis is a data mining method that finds items occurring together, such as products bought in the same basket, and expresses them as association rules.

Affinity capture

Affinity capture is a biochemical method that enriches a target protein or complex from cell extract using an antibody or affinity tag on a solid medium.

Affinity chromatography

Affinity chromatography, also called affinity purification, is a liquid chromatography technique that separates biomolecules by reversible binding to an immobilized ligand, widely used to purify antibodies.

Affinity group

Affinity group: people linked by a common purpose, identity, or interest. Covers activist cells of 5-20 people from Spanish anarchism and 1970s anti-nuclear action, and workplace employee resource groups born from 1960s race-based caucuses, plus legal and research uses.

Affinity labeling

Affinity labeling covalently tags a biomolecule's binding site using a reactive analog of its ligand, identifying binding partners, drug targets, and active-site residues; in its photoaffinity form, light activates the probe.

Affinity Photo

Affinity Photo is a professional raster image editor developed by Serif in Nottingham, first released in 2015 as a layer-based, non-subscription alternative to Adobe Photoshop.

Affinity precipitation

Affinity precipitation is a bioseparation method that selectively precipitates a target protein by binding it to a stimuli-responsive polymer, releasing it by changing pH, salt, or temperature.

Affinity propagation

Affinity propagation is a clustering algorithm, introduced by Frey and Dueck in 2007, that exchanges messages between data points to find exemplars without a preset cluster count.

Affinity Publisher

Affinity Publisher is a desktop publishing and page layout application by the British company Serif, part of the Affinity suite and an alternative to Adobe InDesign.

Affinity purification–mass spectrometry

Affinity purification–mass spectrometry (AP-MS) is a method for identifying protein–protein interactions in which a bait protein is purified from cells with its binding partners and identified by mass spectrometry.

Affinivax

Affinivax was a Cambridge, Massachusetts biotech founded in 2014 to develop vaccines on its MAPS platform, acquired by GSK in 2022 for $2.1 billion upfront.

Sep 19, 2026

Affirm

Affirm is an American financial technology company founded by PayPal co-founder Max Levchin in 2012 that lets consumers split purchases into installment loans with no late fees, trading on Nasdaq as AFRM.

Oct 21, 2026

AFFIRM trial

AFFIRM trial (NCT00974311): phase 3 study of enzalutamide (MDV3100) versus placebo in 1,199 men with metastatic castration-resistant prostate cancer after docetaxel; median survival 18.4 vs 13.6 months. Distinct from the atrial fibrillation AFFIRM trial.

Affirmation (Savage Garden album)

Affirmation is the second and final studio album by Australian pop duo Savage Garden, released November 9, 1999 on Sony. Written remotely by Darren Hayes and Daniel Jones, produced partly by Walter Afanasieff, it reached No. 6 in the US.

Affirmative action

Affirmative action, also known as positive discrimination, is a set of policies to remedy discrimination in admissions, employment, and contracting; the Supreme Court curtailed race-conscious admissions in 2023.

Affirmative action in the United States

Affirmative action in the United States: employment and admissions policies for federal contractors and universities. Key facts: Executive Order 11246 (1965, revoked 2025), Bakke, Grutter, and the 2023 SFFA ruling ending race-conscious college admissions.

Affirmative defense

Affirmative defense: a legal defense in which the defendant, even after the alleged acts are proven, avoids liability by proving matters such as self-defense, duress, insanity, necessity, or entrapment; the party raising it bears the burden of proof, typically by a preponderance of the evidence.