x2
+ x-axis
+ xerography
+ 1938, Carlson and xerography
+ x-rays
+ 1895, Rontgen and x-rays

y2
+ a technology company, Yahoo!
+ 1994, Yang, Filo, and Yahoo!
+ yin and yang
+ 305 BC-240 BC, Zou, and the yin and yang
+ a lumber yard
+ navy yard
+ the headquarters of the Metropolitan Police, Scotland Yard
+ 1829, London and the Scotland Yard
+ stifled a yawn
+ y-axis
+ x-axis and y-axis
+ year-day-month, YDM
+ 365 days in a year
+ 52 weeks in a year
+ Jan., Feb., Mar.; the first 3 months of the year
+ Oct., Nov., Dec.; the last 3 months of the year
+ Apr., May., Jun.; the second 3 months of the year
+ Jul., Aug., Sep.; the third 3 months of the year
+ a banner year
+ a year with an extra day(Feb. 29th), leap year
+ 366 days in a leap year
+ Chinese New Year
- off year
- old year
+ school year
+ solar year
+ the closing days of the year
+ the latter half of the year
+ a vintage year
+ YDM, year-day-month
+ YMD, year-month-day
+/- in after years
+ for years
- have not spoken French for years
+ will last for years
- have been waiting for years
+ looks younger than his years
+ in the intervening years
- lean years
+ to spread the payments over ten years
+ over the years
+ a leavening agent, yeast
+ Mr. Yes
- yes, yes, yes
+ saw him only yesterday
- the town yielded
+ Young Men's Christian Association, YMCA
+ 1844, G. Williams and the YMCA
+ year-month-day, YMD
+ a physical and mental exercise, yoga
+ c. 600 BC, India and yoga
+ egg yolk
+ to bind the mixture with egg yolk
+ a song, New York, New York
+ 1977, Ebb, Kander, and New York, New York
+ upstate New York
+ bless you
+/- no call for you
+ a challenge, "Ask not what your country can do for you."
+ 1961, President Kennedy and "Ask not what your country can do for you."
+ Good for you!
+ to let us hear from you
x fuck you
+ mind you
+ caught a glimpse of you
+ so pleased to see you
+ to thank you
+ to you
+ a song, Happy Birthday to You
+ 1912, Hill Sisters and Happy Birthday to You
+ over to you
+ a pleasure to talk to you
+ to agree with you
+ with young
+ sincerely yours
+ to love your neighbor as yourself
+ to behave yourself
+ to prove yourself
+ to watch yourself
+ the secret of youth
+ a video-sharing website, YouTube
+ 2005, Hurley, Chen, Karim, and YouTube
+ a toy, yo-yo
+ 1928, Flores and the yo-yo
+ Young Women's Christian Association, YWCA
+ 1855, Kinnaird, Robarts, and the YWCA

z2
+ New Zealand
+ an animal of the horse family, zebra
+ Africa and zebras
+ an aquarium fish, zebrafish
+ Himalayan region and zebrafish
+ at its zenith
+ a number, zero
+ c. 650, India and the zero
+ a fastener, zipper
+ 1893, Judson and the zipper
+ based on a 12-month cycle, the zodiac
+ late 500 BC, Babylon and the zodiac
+ based on a 12-year cycle, the Chinese zodiac
+ Aries, Taurus, Gemini, Cancer; first 4 signs of the zodiac
+ Rat, Ox, Tiger, Rabbit; first 4 signs of the Chinese zodiac
+ Leo, Virgo, Libra, Scorpio; middle 4 signs of the zodiac
+ Dragon, Snake, Horse, Goat; middle 4 signs of the Chinese zodiac
+ Sagittarius, Capricorn, Aquarius, Pisces; last 4 signs of the zodiac
+ Monkey, Rooster, Dog, Pig; last 4 signs of the Chinese zodiac
+ buffer zone
+ demilitarized zone
+ kissing zone
+ strike zone
+ Temperate Zone
+ time zone
- war zone
- shingles, herpes zoster