Plural of Nucleus

The Quick Answer

The plural of nucleus is nuclei.

The Plural of Nucleus

The plural of nucleus is nuclei. The alternative plural nucleuses is extremely rare but still acceptable.

Cell nuclei contain most of the cell's genetic material.
Some eukaryotic cell types have no nuclei.
Some cell types have many nucleuses.

The noun nucleus has a Latin root, which is the derivation of the plural nuclei. Nucleuses (which adheres to the standard rules for forming plurals) is also an accepted plural.

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The Standard Rules for Forming the Plurals

The table below shows the standard rules for forming the plurals of nouns in English.

Type	Example of Type	Forming the Plural	Plural
Most Nouns	lamp scythe	add s	lamps scythes
Noun Ending s, sh, ch, x or z	nucleus dress	add es	nucleuses dresses
Nouns ending [consonant] o	hero zero tomato	add either s or es (There are no rules for this - you have to know.)	heroes zeros tomatoes
Nouns ending [vowel] o	patio ratio	add s	patios ratios
Nouns ending [consonant] y	story penny	change the y to an i and add es	stories pennies
Nouns ending [vowel] y	donkey chimney	add s	donkeys chimneys
Nouns ending f or fe	dwarf hoof	ves and/or s (There are no rules - you have to know.)	dwarfs hooves or hoofs
Exceptions	man louse	some nouns undergo a vowel or letters change	men lice
More exceptions	salmon sheep	some nouns do not change at all	salmon sheep
Foreign rulings	nucleus medium	some nouns adopt foreign rulings	nuclei media

Why Is There Confusion over the Plural of Nucleus?

Confusion arises over the plural of nucleus because its original plural form (nuclei) derives from Latin and native English speakers are drawn to nucleuses, which adheres to the standard ruling for forming plurals.

Nuclei is by far the more common plural of the two. (See the difference in Google's Ngram Viewer.)

Another Interactive Exercise

Here are three randomly selected questions from another exercise on plurals, which can be edited, printed to create an exercise worksheet, or sent via email to friends or students.

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