n. pl. pen·i·cil·li·ums or pen·i·cil·li·a (-sĭlē-ə)
Any of various characteristically bluish-green fungi of the genus Penicillium that grow as molds on decaying fruits and ripening cheese and are used in the production of antibiotics such as penicillin and in making cheese.
[New Latin Pēnicillium, genus name, from Latin pēnicillus, brush; see PENCIL.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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:
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.