Y2k
Y2k is short for the year 2000 bug or the millennium bug. Y2k is a warning first published by Bob Bemer in 1971 describing the issues of computers using a two-digit year date stamp.
Ymodem
A ymodem is a file-transfer protocol developed by Chuck Forsburg, that is similar to the enhanced 1k version of xmodem. Ymodem sends data in 1024-byte blocks, allows for multiple file transmissions at once, performs cyclic redundancy checks (crc), and can reduce the transfer size to compensate for poor connections.
Yottabyte
Yottabyte is abbreviated as yb. A yottabyte is equal to 1,208,925,819,614,629,174,706,176 (280) bits, or 1,000,000,000,000,000,000,000,000 (1024) bytes and is the largest recognized value used with storage.