### Definition of Antiparallel

1. Adjective. (especially of vectors) parallel but oppositely directed. "Antiparallel vectors"

Similar to: Parallel

### Definition of Antiparallel

1. a. Running in a contrary direction.

### Definition of Antiparallel

1. Adjective. (mathematics) of vectors, parallel but of opposite direction ¹

2. Adjective. (biochemistry) describing the orientations of the two strands of DNA ¹

3. Adjective. (biochemistry) describing two beta strands comprising a protein's secondary structure that are aligned and hydrogen bonded but the vector describing the amino- and carboxy-terminal ends of each strand are oriented 180° relative to one another. ¹

4. Noun. (geometry) A line that forms equal angles with two other lines, but in opposite directions. ¹

¹ Source: wiktionary.com

### Medical Definition of Antiparallel

1. Straight lines or planes which make angles in some respect opposite in character to those made by parallel lines or planes. Can be used to refer to the two strands of DNA that align in a helical fashion. (01 Mar 2008)

### Lexicographical Neighbors of Antiparallel

 antioxidantsantioxidationantioxidativeantioxidizeantioxidizedantioxidizesantioxidizingantioxygenantioxygenicantiozonant antiozonantsantipainantipapalantipaparazziantiparallel (current term)antiparallel strandantiparallellyantiparallelogramantiparallelogramsantiparallels antiparalyticantiparalyticalantiparalyticsantiparamilitaryantiparasiteantiparasiticantiparasitic agentsantiparasitics

### Literary usage of Antiparallel

Below you will find example usage of this term as found in modern and/or classical literature:

1. A Treatise on the Analytical Geometry of the Point, Line, Circle, and Conic by John Casey (1893)
"... so that the triangle ODE is inversely similar to CBA is called an antiparallel to the base. 9. If la + mß + ny be antiparallel to 7, prove that 10. ..."

2. Modern Geometry of the Point, Straight Line, and Circle: An Elementary Treatise by John Alexander Third (1898)
"and, conversely, if the sides of a triangle and the sides of an inscribed triangle are antiparallel with respect to the angles of the first, the inscribed ..."

3. An Elementary Treatise on Modern Pure Geometry by Robert Lachlan (1893)
"It is obvious that when YZ is antiparallel to BC, the points Y, Z, B, C are concyclic; and that the line through A antiparallel to BC is the tangent at A to ..."

4. Verslagen en Mededeelingen by Koninklijke Nederlandse Akademie van Wetenschappen Afdeling Natuurkunde (1884)
"De raaklijn in het punt P aan de gelijkzijdige hyperbool H (OA, OB; P) is de lijn door P antiparallel aan OP getrokken." Laat men in fig. l het punt Q langs ..."

5. Plane Geometry by William Betz, Harrison Emmett Webb, Percey Franklyn Smith (1912)
"Then FG, the new position of ED, is said to be antiparallel ... Give all the proportions which arise when FG is antiparallel to BC. 14. ..."