三
サン, ゾウ, み, み.つ, みっ.つ, か, さ, さい, さえ, さぶ, ざ, ざえ, ざぶ, そう, ぞ, ただ, みつ, みん, も, や

three

JLPT5 G1 S3 F14

Three slender lines = *three*. In Chinese, "three" often suggests a group, or many; compare this sense in the cognate terms 參 and 森.

[Full Kanji Etymology List]