latus rectum
RareTechnical/Mathematical
Definition
Meaning
A fixed line segment through the focus of a conic section (parabola, ellipse, or hyperbola), perpendicular to its principal axis.
In geometry, the chord through a focus of a conic section parallel to the directrix; a specific parameter defining the width of a conic at its focus.
Linguistics
Semantic Notes
This term is used exclusively in geometry and conic sections. It is a fixed, measurable property of a given conic. The plural is 'latera recta'.
Dialectal Variation
British vs American Usage
Differences
No difference in meaning. Spelling conventions (e.g., 'foci' vs. 'focuses') may follow regional preferences in mathematical texts, but 'latus rectum' itself is invariant.
Connotations
Purely technical with no regional connotative differences.
Frequency
Equally rare in both UK and US academic/technical contexts.
Vocabulary
Collocations
Grammar
Valency Patterns
The latus rectum of [conic section] is [value].Calculate/find/determine the latus rectum.Vocabulary
Synonyms
Neutral
Weak
Usage
Context Usage
Business
Not used.
Academic
Used exclusively in advanced mathematics, physics, and engineering textbooks and papers dealing with conic sections.
Everyday
Not used.
Technical
Central term in geometric calculations, orbital mechanics (describing orbits), and optical design.
Examples
By CEFR Level
- The latus rectum is a key measurement in the geometry of curves.
- To fully describe the parabola, one must determine the coordinates of its vertex, focus, directrix, and the length of its latus rectum.
- In orbital mechanics, the semi-latus rectum is a more commonly used parameter than the full latus rectum.
Learning
Memory Aids
Mnemonic
"Latus" sounds like 'lateral' (side), and "rectum" is Latin for 'straight'—think of a straight line to the side of the focus.
Conceptual Metaphor
A ruler placed at the narrowest/widest point of a curved shape to measure its 'width' at that specific location.
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Avoid literal translation ('прямая кишка') which is anatomically incorrect. The correct mathematical term is 'фокальный параметр' or 'латус ректум' (transliterated).
Common Mistakes
- Mispronouncing 'rectum' with an /ɪ/ sound (as in 'rectify'); it is /ˈrɛktəm/.
- Using it as a plural ('latera rectums' instead of 'latera recta').
- Confusing it with the semi-latus rectum (half its length).
Practice
Quiz
What is the latus rectum of a conic section?
FAQ
Frequently Asked Questions
No, it is an exclusively technical term from geometry and related fields like physics and engineering.
The correct plural is 'latera recta', following its Latin origins.
The semi-latus rectum is exactly half the length of the latus rectum. It is a more frequently used parameter in fields like celestial mechanics.
It may appear in advanced high school or pre-university courses focusing on conic sections, but it is not a core term for general mathematics.