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

Examples of thulium in a Sentence

Recent Examples on the Web The extra proton changes the erbium atom to thulium and release energy. Bayarbadrakh Baramsai, IEEE Spectrum, 27 Feb. 2022 Even the rarest rare earth, thulium, with atomic number 69, is 125 times more common than gold. Stanley Merzman, Discover Magazine, 21 Aug. 2018 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 examples are programmatically compiled from various online sources to illustrate current usage of the word 'thulium.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

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 23 Jun. 2024.

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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