Meaning & readings

nucleus, core, kernel

On’yomi カク

Origin

The character combines the wood radical on the left, which classifies this as something related to trees or plant material, with the component 亥 on the right, which serves as a sound hint for the pronunciation. The character originally depicted the hard pit or stone at the center of a fruit—the kind you'd find in a peach or apricot from a tree. Over time, the meaning expanded from the physical seed pit to the more abstract sense of a core or central part of anything, including the nucleus of a cell or the kernel of an idea.

AI-generated (claude-haiku-4-5), not yet reviewed. Formation type (automated guess): Phono-semantic (meaning + sound hint).

10 strokes

Components

  • radical left
  • sound hint right

A sound hint component points at the character’s pronunciation, not its meaning — don’t read a meaning into it.

Common words

  • 核酸 かくさん nucleic acid
  • 核心 かくしん core; heart (of the matter)
  • 結核 けっかく tuberculosis; TB
  • 中核 ちゅうかく kernel; core
  • 核家族 かくかぞく nuclear family
  • 核実験 かくじっけん nuclear (bomb) test
  • 核弾頭 かくだんとう nuclear warhead
  • 核燃料 かくねんりょう nuclear fuel

Reference

Strokes
10
Kangxi radical
75
Grade
Jōyō (secondary school)
Frequency rank
#475 (newspapers)
Former JLPT
level 1
Unicode
U+06838