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di·thi·o·nous acid (dī-thīə-nəs)

An unstable acid, H₂S₂O₄, that is found chiefly in the form of its salts and is used as a bleaching and reducing agent. Also called hydrosulfurous acid.

[DI-¹ + Greek theion, sulfur + -OUS.]

Indo-European & Semitic Roots Appendices

Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

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Semitic Roots

The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.

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