Definition

1. Adjective:
   • Capable of being split or divided along a natural line of cleavage: This describes a material, especially wood or certain minerals, that can be easily split or cleaved along its grain or natural planes of separation.
   • Capable of undergoing nuclear fission: This describes a material, typically an atomic nucleus or a substance like uranium-235, that can sustain a nuclear fission chain reaction, where the nucleus splits into smaller parts, releasing energy.

Usage Examples

• Adjective (Capable of being split):
  • The geologist identified the rock as fissile shale.
  • Fissile wood like cedar is ideal for making roofing shingles.
• Adjective (Capable of nuclear fission):
  • Uranium-235 is a fissile isotope used in nuclear reactors.
  • The reactor core contains fissile material that sustains the chain reaction.

Advanced Usage

• "Fissile nucleus": A specific atomic nucleus that can undergo fission when struck by a neutron.
  • Plutonium-239 has a fissile nucleus.
• "Readily fissile": Emphasizes how easily a material can be split.
  • The slate was readily fissile, breaking into thin, flat sheets.

Variants and Related Words

• Fissionable (adjective): Often used interchangeably with the nuclear sense of "fissile," meaning capable of undergoing nuclear fission. However, in technical contexts, "fissile" often specifically means fissionable by thermal (slow) neutrons.
  • Both fissile and fissionable materials are heavily regulated.
• Fissility (noun): The property or quality of being fissile.
  • The fissility of the sediment made it easy to study the geological layers.

Synonyms

• For "capable of being split": Cleavable, splittable, divisible.
• For "capable of nuclear fission": Fissionable.

Antonyms

• For "capable of being split": Non-fissile, solid, unbreakable.
• For "capable of nuclear fission": Non-fissile, non-fissionable, fertile (in nuclear physics, a fertile material like uranium-238 can be converted into a fissile material but is not itself fissile by thermal neutrons).

Adjective

1. capable of being split or cleft or divided in the direction of the grain
   • fissile crystals
   • fissile wood
2. capable of undergoing nuclear fission
   • a fissionable nucleous
   • fissionable material