| y | Greek letter psi; wave function |
|---|---|
| Y/A | years of age |
| y/o | years old |
| YA | Yersinia arthritis |
| YAC | yeast artificial chromosome |
| YACP | young adult chronic patient |
| YADH | yeast alcohol dehydrogenase |
| YAG | yttrium aluminum garnet [laser] |
| Yb | ytterbium |
| YBOCS | Yale-Brown Obsessive Compulsive Scale |