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sig·ma

(sĭgmə)

1. The 18th letter of the Greek alphabet. See Table at alphabet.

2. A sigma factor.

3. Statistics The standard deviation of a given probability distribution or a given set of data.

[Greek sīgma, of Phoenician origin; see smk in the Appendix of Semitic roots.]

sigmate′ (-māt′) adj.

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:

Indo-European Roots

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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