陰莖（penis-拉丁語 尾）是一個含勃起組織的圓柱形的器官。說得更精確一點就是，在陰莖內，有3條縱貫全長的長形海綿體，兩條長形的海綿體平行排列在上方，叫陰莖海綿體；一條沿著下方排列，為尿道海綿體。後者含有尿道（尿液和精液排出時經過的管道）。

The External Sex Organs: The Penis

The penis (lat. tail) is a cylindrical organ which contains erectile tissue. To be more precise, there are three elongated spongy bodies inside the penis which extend through its entire length-two running parallel on top (the two corpora cavernosa) and one running along the underside (the corpus spongiosum). This latter body contains the urethra (the duct through which urine and semen are released).