The hard stone or pit at the center of a fruit (a seed/pip).
桃の核をナイフで割って取り出した。
I split the peach pit with a knife and took it out.
さくらんぼの核は小さいが、うっかり飲み込むと危ない。
Cherry pits are small, but it's dangerous to swallow one by accident.
果物を食べる前に核を取り除いてください。
Please remove the pit before eating the fruit.
The core or nucleus of an organization, group, or system; the central or most important part.
彼はチームの核となって若手を引っ張っている。
He is the core of the team and is leading the younger members.
このプロジェクトの核は技術力の向上だ。
The core of this project is improving technical capabilities.
地域活性化の核となるアイデアを出そう。
Let's come up with ideas that will serve as the nucleus for regional revitalization.
Used as a short form for nuclear weapons (i.e., 'nuclear' referring to atomic weapons).
その国は核を保有していると疑われている。
That country is suspected of possessing nuclear weapons.
核の脅威をめぐって国際会議が開かれた。
An international conference was held regarding the nuclear threat.
In physics: the nucleus of an atom (the part composed of protons and neutrons).
原子の核は陽子と中性子でできている。
An atomic nucleus is made up of protons and neutrons.
In biology: the nucleus of a cell (the part containing genetic material).
細胞の核にはDNAが入っている。
The cell nucleus contains DNA.
In meteorology: a condensation nucleus — a particle around which water vapor condenses.
微粒子が雲の凝結核として働くことがある。
Particles can act as condensation nuclei for clouds.
In astronomy: the core of a planet or celestial body (its central region).
地球の核は内核と外核に分かれている。
The Earth's core is divided into an inner core and an outer core.
In chemistry: a ring or central structural unit in a cyclic compound (e.g., an aromatic nucleus).
この化合物はベンゼン核を持つ。
This compound contains a benzene nucleus (benzene ring).
In mathematics: the kernel (set of elements mapped to zero), i.e., the core/null space of a linear map.
線形写像の核が零ベクトルだけなら、その写像は単射だ。
If the kernel of a linear map contains only the zero vector, the map is injective.
The nucleus used in cultured pearls — a small bead placed in the center around which nacre forms.
養殖真珠は小さな核を入れて育てられる。
Cultured pearls are grown by inserting a small nucleus.