4 sentences

1. 他画了一个正方形。

   tā huà le yī gè zhèng​fāng​xíng.

   He drew a square.

   Source: Dong Chinese Dictionary

2. 正方形有四条边。

   zhèng​fāng​xíng yǒu sì tiáo biān.

   A square has four sides.

   Source: Tatoeba

3. 正方形的每个顶点都是直角。

   zhèng​fāng​xíng de měi gè dǐng​diǎn dōu shì zhí​jiǎo.

   Each vertex of a square is a right angle.

   Source: Dong Chinese Dictionary

4. 三角形和正方形都属于几何图形。

   sān​jiǎo​xíng hé zhèng​fāng​xíng dōu shǔ​yú jǐ​hé tú​xíng.

   Triangles and squares are both geometric shapes.

   Source: Dong Chinese Dictionary