Definition

1. Noun:
   • An angle of 180 degrees: A straight angle is a perfectly flat angle formed by two rays that point in exactly opposite directions, creating a straight line.

Usage

• The term "straight angle" is used primarily in geometry and mathematics to describe a specific angular measurement.
• It is a singular, countable noun (e.g., , ).

Examples

• Noun:
  • The two hands of a clock form a straight angle at 6 o'clock.
  • A straight angle is exactly twice the measure of a right angle.
  • When you turn around completely, you have rotated through a straight angle.

Advanced Usage

• "To form a straight angle": When two lines or rays extend from a common point in opposite directions.
  • The two streets form a straight angle at the intersection.
• "To measure a straight angle": To determine that an angle is 180 degrees.
  • The protractor confirmed the line was a straight angle.

Variants and Related Words

• Straight (adj): Extending uniformly in one direction; without a curve or bend. (e.g., ).
• Angle (n): The space between two intersecting lines or surfaces at or close to the point where they meet.

Synonyms

• 180-degree angle: The literal description of its measure.
• Flat angle: An informal synonym emphasizing its visual appearance as a flat line.

Antonyms

• Acute angle: An angle less than 90 degrees.
• Right angle: An angle of exactly 90 degrees.
• Obtuse angle: An angle greater than 90 degrees but less than 180 degrees.
• Reflex angle: An angle greater than 180 degrees but less than 360 degrees.

Related Phrases and Concepts

• Supplementary angles: Two angles whose measures add up to 180 degrees. A straight angle is the sum of two supplementary angles.
  • If one angle is 120 degrees, its supplementary angle is 60 degrees, and together they form a straight angle.
• Linear pair: A pair of adjacent angles whose non-common sides are opposite rays, forming a straight angle.
  • Angles 1 and 2 are a linear pair, so their sum is a straight angle.

Noun

1. an angle of 180 degrees