What Is the Plural of Genus?

A genus is a group of objects that have similar characteristics. You may be most familiar with the word genus from biology class, as it refers to the subdivision in the classification of organisms. If you want to refer to more than one genus, you can use a few forms.

Both "genera" and "genuses" are correct, although "genera" is best for academic writing. Note: You pronounce genera as JEN - er - uh.

Awkward Plurals

Pluralizing words is not something you stress about when preparing to write a paper. You just add an “s” or maybe an “es,” right? Well, sometimes it is not that easy. As you write, you may come across a word that you just do not know how to make plural. There are many words that just do not fit into our standard idea of making a singular word into a plural one. These kinds of nouns are called irregular plural nouns. 

Irregular plural nouns can take many forms. Some of them change just the last few letters. Some change vowels in the middle of the word. Some nouns do not even change at all. There is not an easy trick to remember most of them, you just have to learn and memorize them. Below we will look at some commonly confused plural forms of words. There are some words or phrases that can be a bit tricky as well:

• Attorney general to attorneys general
• Passerby to passersby
• Sister in law to sisters in law
• Coat of arms to coats of arms

Plurals That Take No Change

Some words do not have different forms when singular or plural. For example:

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What Are Plural Nouns in Grammar?

By Richard Nordquist

• Pants
• Deer
• Corps
• Fish
• Sheep
• Offspring
• Shrimp
• Moose
• Scissors

Words That Add "S"

Some words that end in “o” can either just have an “s” or an “es” added to the end:

• Potato to potatoes
• Memo to memos
• Hero to heroes
• Volcano to volcanoes
• Tomato to tomatoes

Words That Take an "I"

Next are some words that end in “i” when pluralized. These words usually come from Latin or other languages. Here are some examples that you may encounter in your writing:

• Syllabus becomes syllabi
• Fungus becomes fungi
• Nucleus becomes nuclei
• Radius becomes radii
• Alumnus becomes alumni
• Stimulus becomes stimuli
• Cactus to cacti
• Focus to foci

Words That Change Completely

Then, of course, there are words that just change. Some of these are Latin or Greek based as well:

• Die to dice
• Millennium to millennia
• Bacterium to bacteria
• Criterion to criteria
• Curriculum to curricula
• Parenthesis to parentheses 
• Emphasis to emphases
• Thesis to theses
• Appendix to appendices
• Analysis to analyses 
• Synopsis to synopses
• Genus to genera
• Ox to oxen
• Hypothesis to hypotheses 

Words That Replace "F" With "V"

Sometimes if a word ends in “f” or an “f” sound, we replace it with a “v” before adding the “es”:

• Wife to wives
• Calf to calves
• Life to lives
• Thief to thieves
• Leaf to leaves
• Self to selves
• Knife to knives
• Elf to elves
• Shelf to shelves
• Wolf to wolves

Words That Change a Vowel Sound

Another strange way we can change a singular word to plural is by changing the internal vowel sound. Some of these are:

• Man to men
• Woman to women
• Mouse to mice
• Foot to feet
• Tooth to teeth
• Goose to Geese
• Louse to lice