thu·​li·​um ˈthü-lē-əm How to pronounce thulium (audio)
: a soft silvery metallic element of the rare-earth group see Chemical Elements Table

Example Sentences

Recent Examples on the Web The least abundant of these, thulium (Tm) and lutetium (Lu) are 200 times more abundant than gold. Willy Shih, Forbes, 24 Feb. 2021 The 794 nm photon interacts with a lithium-niobate crystal doped with thulium, so that the photon’s state becomes stored in the crystal. Anil Ananthaswamy, Scientific American, 19 June 2019 Electronic shielding by closed shells in thulium compounds. Spencer Reiss, WIRED, 1 May 2004

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'thulium.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History


New Latin, from Latin Thule

First Known Use

1879, in the meaning defined above

Time Traveler
The first known use of thulium was in 1879

Dictionary Entries Near thulium

Cite this Entry

“Thulium.” Dictionary, Merriam-Webster, Accessed 1 Dec. 2022.

Kids Definition



thu·​li·​um ˈth(y)ü-lē-əm How to pronounce thulium (audio)
: a soft rare metallic element see element

Medical Definition



thu·​li·​um ˈth(y)ü-lē-əm How to pronounce thulium (audio)
: a trivalent metallic element of the rare-earth group
symbol Tm
see Chemical Elements Table

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