blas·​to·​cyst ˈbla-stə-ˌsist How to pronounce blastocyst (audio)
: the modified blastula of a placental mammal having an outer layer composed of the trophoblast

Example Sentences

Recent Examples on the Web Bears mate in springtime, but the fertilized egg remains a microscopic blastocyst until late fall when the sow dens up for winter. David James, Anchorage Daily News, 16 July 2022 The researchers then plucked a few cells from among the 300 or so in each blastocyst and established embryonic stem cell lines in the lab. Megan Molteni, STAT, 8 July 2022 The tool integrates with time-lapse imaging (TLI) systems to provide continuous predictions from fertilization to the blastocyst stage. Ganes Kesari, Forbes, 30 June 2022 Of the four embryos that survived to the blastocyst stage, only two were genetically normal. Akhil Sharma, The New Yorker, 24 Jan. 2022 In an advance reported in the New York Times in 1979, Dr. Mintz showed that the cells of a particular kind of tumor, called a teratoma, could be inserted into a normal blastocyst, or early embryo, of a mouse. Emily Langer, Washington Post, 14 Jan. 2022 Embryos that survive to the blastocyst stage stand a good chance of implantation once placed in the uterus. Isabella Cueto, STAT, 30 Nov. 2021 The science journal Nature reports that scientists have created a structure like a blastocyst – an early embryo – using mouse stem cells instead of the usual sperm and egg. Cnn Editorial Research, CNN, 28 May 2021 Under certain culture conditions, the cells can form each of the three cell types in the blastocyst, researchers previously found. Mitch Leslie, Science | AAAS, 17 Mar. 2021 See More

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

Word History


blasto- + -cyst

First Known Use

1876, in the meaning defined above

Time Traveler
The first known use of blastocyst was in 1876

Dictionary Entries Near blastocyst

Cite this Entry

“Blastocyst.” Dictionary, Merriam-Webster, Accessed 9 Dec. 2022.

Medical Definition


blas·​to·​cyst ˈblas-tə-ˌsist How to pronounce blastocyst (audio)
: the modified blastula of a placental mammal

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