When it comes to Latin plurals, we English speakers have a time of it. It isn't just that we borrow without compunction from other languages, but in the process we anglicize those borrowed words in no particular pattern.

As Bill Bryson explains in "The Mother Tongue: English and How It Got That Way," the longer ago we borrowed a word, the more likely we will anglicize it. Contrast the pronunciation of the more recent borrowing of camouflage, for example, with the pronunciation of the more distant borrowing of chief. Of course, as Bryson points out, we liked that word so much we borrowed it a second time, and this more recent borrowing we pronounce chef.

But those Latin plurals — ooh, la, la, they're something else. For example, if algae is the plural form of the Latin word alga, it should be "The algae are getting to be a problem," right? Wrong.

And we know that alumni is the plural form of alumnus, and alumnae is the plural form of alumna, so if algae and alumnae are both plural forms, they should rhyme, right? Wrong.

And if medium is the singular form of media and biennium is the singular form of biennia, then what happened to the singular form of agenda?

And if the plural form of criterion is criteria and the plural form of stratum is strata, then why isn't the plural form of moratorium moratoria? And don't even ask me how many auditoria are in this building or how many octopodes are in the sea. Lots, apparently.

Well, it has been a long time since my three years of Latin in high school, but with a little help from various style guides, I'll venture some guidelines on when to respect Latin plural forms and when to anglicize them. (I can't tell you how much I wanted to write, "when to latinize and when to anglicize.")

Use Latin plural forms for the following words:

Alumna/alumnae, alumnus/alumni, basis/bases, crisis/crises, criterion/criteria, medium/media, nucleus/nuclei, oasis/oases, parenthesis/parentheses, phenomenon/phenomena, synopsis/synopses, thesis/theses

Use anglicized plural forms in everyday English (but Latin forms in scientific, legal and academic writing) for the following words:

Appendix/appendixes (but appendices), aquarium/aquariums (but aquaria), cactus/cactuses (but cacti), compendium/compendiums (but compendia), crematorium/crematoriums (but crematoria), curriculum/curriculums (but curricula), formula/formulas (but formulae), focus/focuses (but foci), helix/helixes (but helices), index/indexes (but indices), matrix/matrixes (but matrices), memorandum/memorandums (but memoranda), referendum/referendums (but referenda), stigma/stigmas (but stigmata), syllabus/syllabuses (but syllabi), vortex/vortexes (but vortices).

And for heaven's sake, if you're talking to more than one professor emeritus, you'd better make it professors emeriti. As for datum and data, increasingly data is being used both for the singular and the plural. Nevertheless, I'm still holding out for data are, although 10 years from now I'm going to start writing data is.

So the next time you're wondering how many hippopotami it takes to make an agendum, give a nod to the Latin roots and take care when you anglicize those plural forms.

And remember: Sometimes it's better to latinize.

Stephen Wilbers offers training seminars in effective business writing. E-mail him at wilbe004@umn.edu. His website is www.wilbers.com.