丸 (Kanji for round)

Onyomi

GAN	GHANDI had round glasses.

This is basically 9 (九)　plus one stroke.
Nine plus one equals ten, which is a round number. Sorry, that's the best I could do.

まる	circle ★★★★☆
まる＊い	circular ★★★★☆

日の丸(ひのまる)	the Japanese flag. ★★☆☆☆ 日 (sun, day) + 丸 (round) = 日の丸 (the Japanese flag.)
弾丸(だんがん)	bullet ★☆☆☆☆ 弾 (bullet / play guitar / bounce) + 丸 (round) = 弾丸 (bullet)

	Meaning	Hint	Radical
刃	blade	SWORD	刀
丸	round	HOOK

Blade comes from the SWORD radical, which makes sense.

'Round' comes from 9, which has a HOOK on the right side. (the right side of blade turns outwards).

So you can say, "I can hang nine round donuts on the HOOK."