Definition

1. Noun:

   • Compact Disc: A small, circular, flat object made of plastic and metal used to store digital data, such as music, computer software, or video, which is read by a laser beam.
   • Certificate of Deposit: A type of savings account offered by a bank or credit union with a fixed interest rate and a fixed date of withdrawal (maturity date).
   • Candela: The standard international unit (SI unit) for measuring luminous intensity, which is the power of light as perceived by the human eye.
   • Cadmium: A soft, bluish-white metallic chemical element that is toxic and is often used in batteries, pigments, and metal plating.

2. Adjective:

   • Four hundred: Representing the cardinal number 400. This is an archaic or specialized use, derived from the Roman numeral CD.

Examples of Usage

• Noun (Compact Disc):
  • I bought the new album on cd.
  • The software installation files are stored on a cd-rom.
• Noun (Certificate of Deposit):
  • She invested her savings in a six-month cd to earn a higher interest rate.
• Noun (Candela):
  • The lamp's output is 800 cd. (This technical usage is less common in everyday language.)
• Noun (Cadmium):
  • The yellow pigment contained cd. (This technical usage is almost exclusively scientific.)
• Adjective:
  • The year cdXLIV is 444. (This usage is very rare in modern contexts.)

Advanced Usage

• The term cd is most commonly used as a countable noun for the physical object (the disc). Its other meanings are typically found in specific, technical contexts (finance, physics, chemistry).
• In computing, cd is also a fundamental command in command-line interfaces (like Terminal or Command Prompt) meaning "change directory."

Variants and Related Words

• CD-ROM (noun): A Compact Disc Read-Only Memory, used for storing computer data.
• CD-R (noun): A Compact Disc-Recordable, a blank disc onto which data can be written once.
• CD-RW (noun): A Compact Disc-ReWritable, a blank disc that can be written, erased, and rewritten multiple times.
• CD player (noun): An electronic device for playing audio compact discs.

Synonyms

• For Compact Disc: disc, optical disc.
• For Certificate of Deposit: time deposit, savings certificate.
• For Candela: (No common synonym; it is a standard unit).
• For Cadmium: (Element symbol Cd).

Related Phrases

• "Burn a cd": To write data onto a recordable compact disc.
  • I need to burn a cd with the presentation files.
• "Rip a cd": To copy the audio tracks from a compact disc onto a computer.
  • He ripped his entire cd collection to his hard drive.

Adjective

1. being one hundred more than three hundred

Noun

1. a digitally encoded recording on an optical disk that is smaller than a phonograph record; played back by a laser
2. a debt instrument issued by a bank; usually pays interest
3. the basic unit of luminous intensity adopted under the Systeme International d'Unites; equal to 1/60 of the luminous intensity per square centimeter of a black body radiating at the temperature of 2,046 degrees Kelvin
4. a soft bluish-white ductile malleable toxic bivalent metallic element; occurs in association with zinc ores