Geometry is a kind of mathematics, which studies the size, shapes, and positions of things. There are flat (2D) and solid (3D) shapes in geometry. There are shapes such as squares, circles and triangles in flat geometry, but there are cubes, cylinders, cones and spheres in solid geometry.
Jǐhéxué shì yīzhǒng shùxué, yánjiū shìwù de dàxiǎo, xíngzhuàng hé wèizhì. Jǐhéxué yǒu píngmiàn (2D) hé lìtǐ (3D) de xíngzhuàng. Píngmiàn jǐhé yǒu zhèngfāngxíng, yuánxíng hé sānjiǎoxíng děng xíngzhuàng, ér lìtǐ jǐhé yǒu lìfāngtǐ, yuánzhùtǐ, yuánzhuītǐ hé qiútǐ děng.