| n. | 1. | the chemical symbol for erbium, a rare earth element. It has atomic number 68 and an atomic weight of 167.26. |
| Noun | 1. | Er - a trivalent metallic element of the rare earth group; occurs with yttrium Synonyms: atomic number 68, erbium |
| 2. | ER - a room in a hospital or clinic staffed and equipped to provide emergency care to persons requiring immediate medical treatment Synonyms: emergency room |
| 1. | ER - Entity-Relationship | ||
| 2. | (networking) | er - The country code for Eritrea. |