| Y | Yocto | - | Astronomy |
| Y | Yotta - Yttrium | - | Astronomy |
| Y2K | Year Two Thousand | - | Astronomy |
| YA | Yoctoampere | - | Astronomy |
| YA | Yottaampere -Young Adult | - | Astronomy |
| YA | Yottayear | - | Astronomy |
| YABPR | Yet Another Brother Pat Rant | - | Astronomy |
| YAC | Youth-Adult Committee | - | Astronomy |
| YAP | Young Aspiring Professional | - | Astronomy |
| YB | Youcef Benzouada (Southern Algerian Name) | - | Astronomy |
| YB | Ytterbium | - | Astronomy |
| YC | Yoctocoulomb | - | Astronomy |
| YC | Yottacoulomb | - | Astronomy |
| YD | People's Democratic Republic Of Yemen (ISO 3166 Digram | - | Astronomy |
| YE | Yemen (ISO 3166 Digram) | - | Astronomy |
| YEM | Yemen (ISO 3166 Trigram) - Manitowaning/Manitoulin East Municipal Airport IATA Airport Code | - | Astronomy |
| YER | Yemeni Rial (ISO 4217 Currency Code) | - | Astronomy |
| YF | Yoctofarad | - | Astronomy |
| YF | Yottafarad | - | Astronomy |
| YG | Yoctogram | - | Astronomy |
| YG | Yottagram | - | Astronomy |
| YGCO | Yamaneko Group Of Comet Observers | - | Astronomy |
| YGO | Yu-Gi-Oh! | - | Astronomy |
| YH | Yoctohenry | - | Astronomy |
| YH | Yottahenry | - | Astronomy |
| YHBT | You Have Been Trolled | - | Astronomy |
| YI | Serbia And Montenegro (deprecated FIPS 10-4 Country Code | - | Astronomy |
| YI | Yiddish Language (ISO 639-1 Code) | - | Astronomy |
| YI | Yobi | - | Astronomy |
| YID | Yiddish Language (ISO 639-2 Code) | - | Astronomy |
| YIPPIE | Youth International Party + Suffix | - | Astronomy |
| YJ | Yoctojoule | - | Astronomy |
| YJ | Yottajoule | - | Astronomy |
| YK | Yoctokelvin | - | Astronomy |
| YK | Yottakelvin | - | Astronomy |
| YL | Yoctolitre | - | Astronomy |
| YL | Yottalitre | - | Astronomy |
| YM | Yemen (FIPS 10-4 Country Code) -Your Magazine (originally Young Miss | - | Astronomy |
| YM | Yoctometre | - | Astronomy |
| YM | Yottametre | - | Astronomy |
| YMCA | Young Men's Christian Association | - | Astronomy |
| YMD | People's Democratic Republic Of Yemen (ISO 3166 Trigram | - | Astronomy |
| YMMV | Your Mileage May Vary | - | Astronomy |
| YN | Yoctonewton | - | Astronomy |
| YN | Yottanewton | - | Astronomy |
| YO | Former Yugoslavia (NATO Country Code | - | Astronomy |
| YO | Yoruba Language (ISO 639-1 Code) | - | Astronomy |
| YOR | Yoruba Language (ISO 639-2 Code) | - | Astronomy |
| YPA | Yards Per Pass Attempt (football Statistic) | - | Astronomy |
| YS | Yoctosecond | - | Astronomy |
| YS | Yoctosiemens | - | Astronomy |
| YS | Yottasecond | - | Astronomy |
| YS | Yottasiemens | - | Astronomy |
| YSA | Youth Service America - Young Socialist Alliance | - | Astronomy |
| YSI | Young Scots For Independence | - | Astronomy |
| YT | Mayotte (ISO 3166 Digram) - Yottatesla - Yukon Territory (postal Symbol) | - | Astronomy |
| YT | Yoctotesla | - | Astronomy |
| YTD | Year-To-Date | - | Astronomy |
| YTM | Yield To Maturity | - | Astronomy |
| YTS | Youth Training Scheme | - | Astronomy |
| YU | York University -former Yugoslavia (ISO 3166 Digram | - | Astronomy |
| YUG | Former Yugoslavia (ISO 3166 Trigram | - | Astronomy |
| YUPPIE | Young Urban Professional + Suffix | - | Astronomy |
| YV | Yoctovolt | - | Astronomy |
| YV | Yottavolt | - | Astronomy |
| YW | Yoctowatt | - | Astronomy |
| YW | Yottawatt | - | Astronomy |
| YWCA | Young Women's Christian Association | - | Astronomy |
| YYH | YuYu Hakusho | - | Astronomy |
