What does it mean for the three persons of the Trinity to be one in substance if the divine nature has no material body?

Also, are substance and nature the same thing in this context?

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DAVIDIVS DOCTVS VTRIVSQVE LINGVAE
Husband of Emilia
Member: First Reformed Presbyterian Church of Durham (RPCNA) - Durham, NC
Currently in the process of transferring membership to an as-yet-undecided church in Chapel Hill
Student: University of North Carolina at Chapel Hill, German Literature and Classics