Definition

1. Noun:
   • The unit of solid angle adopted under the Systeme International d'Unites: "sr" is the abbreviation for the steradian, the SI unit for measuring solid angles.
   • A soft silver-white or yellowish metallic element of the alkali metal group; turns yellow in air; occurs in celestite and strontianite: "Sr" is the chemical symbol for the element strontium.

Usage Examples

• Noun (Unit of Measurement):

  • The solid angle subtended by a sphere at its center is 4π sr.
  • The luminous intensity is measured in candela per steradian (cd/sr).

• Noun (Chemical Element):

  • Sr-90 is a radioactive isotope of strontium.
  • The compound contains atoms of Sr and O.

Advanced Usage

• In scientific contexts: "sr" is almost exclusively used in technical writing, particularly in physics, mathematics, and engineering, to denote the steradian.
• In chemical formulas and notation: "Sr" is used in chemical equations, periodic tables, and material science to represent the element strontium.

Variants and Related Words

• Steradian (n): The full name for the unit "sr".
• Strontium (n): The full name for the element "Sr".

Synonyms

• For the unit: There is no direct synonym for "steradian" as it is a specific SI unit.
• For the element: There is no synonym for the element "strontium".

Notes on Usage

• Capitalization: The unit "sr" (steradian) is written in lowercase. The chemical symbol "Sr" (strontium) is written with a capital 'S' and lowercase 'r'.
• Context is critical: The meaning is entirely dependent on the surrounding text. In a physics paper, "sr" likely means steradian. In a chemistry text, "Sr" likely means strontium.
• It is an abbreviation/symbol: "sr" is not a typical word but a scientific symbol or abbreviation. It is not used in everyday conversation.

Noun

1. the unit of solid angle adopted under the Systeme International d'Unites
2. a soft silver-white or yellowish metallic element of the alkali metal group; turns yellow in air; occurs in celestite and strontianite