|an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.|
|a calculus or concretion found in the stomach or intestines of certain animals, esp. ruminants, formerly reputed to be an effective remedy for poison.|
lanthanide lan·tha·nide (lān'thə-nīd')
Any of the chemically related elements with atomic numbers 57 through 71. Also called rare earth, rare-earth element.
|lanthanide (lān'thə-nīd') Pronunciation Key
Any of a series of 15 naturally occurring metallic elements. The lanthanides include elements having atomic numbers 57 (lanthanum) through 71 (lutetium). They are grouped apart from the rest of the elements in the periodic table because they all behave in a similar way in chemical reactions. Also called rare-earth element. See Periodic Table.