A circle; anything round or circular (the shape or symbol '○').
紙に丸を描いて名前の横に付けておいた。
I drew a circle on the paper and put it next to the name.
この公園には丸い噴水がある。
There is a circular fountain in this park.
The entirety or wholesomeness of something; used to mean whole or complete (e.g., 'entirely', 'whole').
リンゴを皮ごと丸ごと食べた。
I ate the apple whole, skin and all.
会社は丸一年かけてプロジェクトを完成させた。
The company completed the project over the course of a full year.
Slang for money; dough (colloquial).
あいつは丸をたくさん持っているらしい（俗語）。
Apparently he has a lot of money (slang).
新しいビジネスで丸を儲けた。
He made a lot of money with the new business.
An enclosure inside a castle's walls — a bailey or inner ward (used in castle terminology).
本丸は城の最も重要な建物がある場所だ。
The honmaru (main bailey) is where the castle's most important buildings are located.
In Kansai dialect, a term sometimes used for the soft‑shelled turtle (regional usage).
関西では昔、『丸』でスッポンを呼ぶことがあったらしい（方言）。
Apparently in Kansai people used to call soft‑shelled turtles 'maru' (dialect).
A suffix used in ship names, people’s names (especially infants), names of swords, instruments, dogs, horses, etc.; commonly seen as '‑maru' at the end of such names.
昔の商船には『二葉丸』のように『丸』が付く名前が多かった。
Old merchant ships often had names ending with '‑maru', like 'Futabamaru'.
幼い子の名前に『丸』を付ける習慣が昔はあった。
There used to be a custom of adding 'maru' to a young child's name.