Free ATI TEAS 7 English & Language Usage guide
October 2026 - Plural Spellings Study Guide for nursing students in
Most plurals add s or es, but words ending in consonant-y change to ies, some ending in f change to ves, and irregulars change form entirely. Medical terms follow Latin and Greek patterns, and those are the ones a nursing exam asks about.
The regular rules
| Ending | Rule | Examples |
|---|---|---|
| Most words | Add s | chart → charts |
| s, x, z, ch, sh | Add es | box → boxes; dish → dishes |
| Consonant + y | Change y to ies | artery → arteries; injury → injuries |
| Vowel + y | Add s | day → days; x-ray → x-rays |
| f or fe | Often change to ves | shelf → shelves; knife → knives |
| Consonant + o | Usually es | potato → potatoes |
The y rule turns on the letter before it. Artery has a consonant before the y, so it becomes arteries; x-ray has a vowel, so it becomes x-rays. Checking that one letter resolves most y-ending questions without any memorisation.
Medical plurals worth learning
These follow Latin and Greek patterns rather than English ones, and they appear constantly in nursing texts.
| Singular | Plural | Pattern |
|---|---|---|
| nucleus | nuclei | -us → -i |
| bacterium | bacteria | -um → -a |
| diagnosis | diagnoses | -is → -es |
| vertebra | vertebrae | -a → -ae |
| phenomenon | phenomena | -on → -a |
| index | indices | -ex/-ix → -ices |
| fungus | fungi | -us → -i |
| prognosis | prognoses | -is → -es |
The irregulars
These change form or do not change at all, and there is no rule — only recognition.
- Vowel changes:
man → men,woman → women,foot → feet,tooth → teeth,goose → geese. - Old endings:
child → children,ox → oxen. - No change:
sheep,deer,series,species. - Watch the singular.
Bacteriaandcriteriaare plurals — the singulars arebacteriumandcriterion, and using the plural as a singular is a common error the exam tests directly.
Working out an unfamiliar plural
Worked example
What is the plural of biopsy?
- Identify the ending: it ends in y.
- Check the letter before the y:
s, a consonant. - Consonant plus y means the y changes to
ies. - So the plural is
biopsies.
Biopsies. The same rule handles artery → arteries, injury → injuries and therapy → therapies — one check on one letter.
Terms to know
- Plural
- The form of a noun meaning more than one.
- Regular plural
- One formed by adding s or es.
- Irregular plural
- One that changes form or does not change at all.
- Latin plural
- A plural following Latin patterns: -us to -i, -um to -a, -a to -ae.
- Greek plural
- A plural following Greek patterns: -is to -es, -on to -a.
- Collective noun
- A word for a group treated as one thing, such as staff or team.
What the TEAS asks most
The same core ideas appear in different wording. If you can answer these without stopping to think, you have what this section requires.
What is the plural of this word?
Check the ending, then the letter before it. Medical terms usually follow Latin or Greek.
Which sentence uses the plural correctly?
Watch for a Latin plural used as a singular — one bacteria, one criteria.
What is the singular of this plural?
Reverse the pattern: bacteria → bacterium, diagnoses → diagnosis, criteria → criterion.
Key points
- Most nouns add s; those ending in s, x, z, ch or sh add es.
- Consonant plus y becomes ies; vowel plus y just adds s.
- Medical terms follow Latin and Greek patterns: nucleus/nuclei, diagnosis/diagnoses, vertebra/vertebrae.
Bacteriaandcriteriaare plurals; the singulars arebacteriumandcriterion.- Some nouns — sheep, series, species — do not change at all.
Review quiz
4 questions on this topic, each with the reasoning worked through. Pick an answer to see how it went, or open the explanation straight away.
-
Question 1 of 4
What is the plural of
diagnosis?Show the answer and explanation
Correct answer: C. diagnoses
Words ending in -is take -es in the plural, giving
diagnoses— the same pattern as prognosis and analysis. Adding an English ending to a Greek word produces the first option, which is never correct. -
Question 2 of 4
Which sentence is correct?
Show the answer and explanation
Correct answer: B. A single bacterium was identified in the sample.
Bacteriais already plural, so a single organism is abacterium— and a singular subject needs the singular verb "was". This mistake is so common in speech that recognising it in writing is exactly what the question tests. -
Question 3 of 4
What is the plural of
therapy?Show the answer and explanation
Correct answer: B. therapies
The letter before the y is a consonant, so it changes to
ies. A vowel before the y — as inx-ray— would mean simply adding s instead, which is why checking that one letter matters. -
Question 4 of 4
Which of these is the correct plural of
vertebra?Show the answer and explanation
Correct answer: B. vertebrae
Latin words ending in -a take -ae, giving
vertebrae. The -i ending belongs to words ending in -us, such as nucleus and fungus, and the English -s ending does not apply to this pattern.
Put this TEAS topic into practice
Build a set on plural spellings and use the rationale on every question to reinforce what you just reviewed.
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