from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A white metallic transuranic element of the actinide series, having isotopes with mass numbers from 237 to 246 and half-lives from 25 minutes to 7,950 years. Its longest-lived isotopes, Am 241 and Am 243, are alpha-ray emitters used as radiation sources in research. Atomic number 95; specific gravity 11.7; valence 3, 4, 5, 6. See Table at element.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The chemical element (symbol Am) with an atomic number of 95.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a radioactive transuranic metallic element; discovered by bombarding uranium with helium atoms
After America .(American Heritage® Dictionary of the English Language, Fourth Edition)
From Americ(as) + -ium, by analogy with europium. (Wiktionary)