10-10-321 is a United States long-distance phone service best known for its prolific television and direct mail advertising in the late 1990s. 10-10-321 was the first mass-marketed service of its type, and it and the similar 10-10-220 and 10-10-987 services were all owned by Telecom USA, which was owned by MCI; MCI is now part of Verizon.

<computer> Programmed Data Processor model 10. The series of mainframes from DEC that made time-sharing real. It looms large in hacker folklore because of its adoption in the mid-1970s by many university computing facilities and research labs, including the MIT AI Lab, Stanford, and CMU. Some aspects of the instruction set (most notably the bit-field instructions) are still considered unsurpassed. The PDP-10 was eventually eclipsed by the VAX machines (descendants of the PDP-11) when DEC recognised that the PDP-10 and VAX product lines were competing with each other and decided to concentrate its software development effort on the more profitable VAX. The machine was finally dropped from DEC's line in 1983, following the failure of the Jupiter Project at DEC to build a viable new model. (Some attempts by other companies to market clones came to nothing; see Foonly and Mars.) This event spelled the doom of ITS and the technical cultures that had spawned the original {Jargon File}, but by mid-1991 it had become something of a badge of honourable old-timerhood among hackers to have cut one's teeth on a PDP-10. See TOPS-10, AOS, BLT, DDT, DPB, EXCH, HAKMEM, JFCL, LDB, pop, push. news:alt.sys.pdp10 [Was the PDP-10 a mini or a mainframe?] (2001-01-05)

10 (ten) is an even natural number following 9 and preceding 11. Ten is the base of the decimal numeral system, by far the most common system of denoting numbers in both spoken and written language.