1A bone — the hard tissue that supports a person's or animal's body; one of the individual pieces that make up the skeleton, rich in calcium.
スキーで転んで足の骨を折ってしまった。
I fell while skiing and broke a bone in my leg.
魚を食べるときは小さな骨に気をつけて。
Watch out for small bones when you eat fish.
カルシウムは骨を丈夫にするために欠かせない。
Calcium is essential for keeping your bones strong.
犬に骨をあげると、嬉しそうに噛み始めた。
When I gave the dog a bone, it happily started chewing on it.
2A frame — the internal structure that holds the shape of an object such as a building, umbrella, folding fan, or kite.
強風で傘の骨が一本折れてしまった。
One of the umbrella's ribs broke in the strong wind.
扇子の骨は竹で作られていることが多い。
The ribs of a folding fan are often made of bamboo.
家の骨ができあがれば、あとは内装を仕上げるだけだ。
Once the frame of the house is up, all that's left is finishing the interior.
3The outline, core, or essential structure of something — the main points or backbone of a story, plan, or argument.
企画書の骨を先に固めてから、細かい点を詰めよう。
Let's nail down the outline of the proposal first, then work out the finer points.
この小説はストーリーの骨がしっかりしている。
This novel has a solid story structure.
4A figurative expression for backbone, spirit, or fortitude — the inner strength to stand up to hardship. Typically appears as 骨がある or 骨のある, used to praise someone's strength of character.
彼は骨のある若者で、困難があっても絶対に諦めない。
He's a young man with real backbone — he never gives up, no matter the difficulty.
今の時代、骨のあるリーダーが求められている。
In today's world, leaders with real backbone are in demand.
5Laborious, troublesome, or taxing — describes work that takes real effort. Used chiefly in the idiom 骨が折れる (to be hard work / a real chore) and in forms like 骨な仕事 or 骨の折れる作業 (demanding task).
この引っ越しは思った以上に骨が折れた。
This move turned out to be much more work than I expected.
役所の手続きは書類が多くて骨が折れる。
Government paperwork is a real chore because there are so many forms.
新人を一から育てるのはなかなか骨の折れる仕事だ。
Training a newcomer from scratch is quite a demanding job.