Merriam-Webster Collegiate Dictionary - sex

 I. noun  Etymology: Middle English, from Latin ~us  Date: 14th century  1. either of the two major forms of individuals that occur in many species and that are distinguished respectively as female or male especially on the basis of their reproductive organs and structures  2. the sum of the structural, functional, and behavioral characteristics of organisms that are involved in reproduction marked by the union of gametes and that distinguish males and females  3.  a. ~ually motivated phenomena or behavior  b. ~ual intercourse  4. genitalia  II. transitive verb  Date: 1884  1. to identify the ~ of ~ newborn chicks  2.  a. to increase the ~ual appeal of — often used with up  b. to arouse the ~ual desires of SEXAGENARIAN  noun  Etymology: Latin sexagenarius of or containing sixty, sixty years old, from sexageni sixty each, from sexaginta sixty, from sex six + -ginta (akin to Latin viginti twenty) — more at six, vigesimal  Date: 1738 a person whose age is in the sixties  • ~ adjective