十 (radical 24, 十+0, 2 strokes, cangjie input 十 (J), four-corner 4000₀, composition ⿻一丨)

Unlike 一, which was one horizontal stroke meaning one, 十 was originally simply a vertical stroke. In later forms 一 was added, forming a cross.

十: Hán Việt readings: thập (寔(thực)入(nhập)切(thiết))^[1][2][3]
十: Nôm readings: thập^[1][2][4]