antiparallel

American  

[an-tee-par-uh-lel, an-tahy-] / ˌæn tiˈpær əˌlɛl, ˌæn taɪ- /

adjective

Mathematics, Physics.

1. (of two vectors) pointing in opposite directions.

---

antiparallel British  

/ ˌæntɪˈpærəˌlɛl /

adjective

1. physics parallel but pointing in the opposite direction

2. maths (of vectors) parallel but having opposite directions

---

Etymology

Origin of antiparallel

First recorded in 1650–60; anti- + parallel

Example Sentences

Wilson continued, "If those magnetic moments interact in a way that wants them to point antiparallel to one another, we call that antiferromagnetism."

From Science Daily • Mar. 16, 2026

The two strands run antiparallel to each other.

From Textbooks • Jun. 9, 2022

On rare occasions the spins of the protons and electrons in neutral hydrogen atoms flip from being parallel to antiparallel, emitting a photon at a frequency of 1.4 gigahertz—the so-called 21-centimter radiation.

From Science Magazine • Jul. 18, 2019

The homology models of KBTBD4Kelch adopt the six-bladed β-propeller fold with each ‘blade’ formed by a four-stranded antiparallel β-sheet.

From Nature • Jul. 18, 2017

The spins of the u and d quarks are antiparallel, enabling the pion to have spin zero, as observed experimentally.

From Textbooks • Aug. 12, 2015