Plural of Basis: Meaning, Grammar Rules, and Examples

Language often creates puzzles, and one of the most common is the plural of basis. Many people guess wrongly because the word looks simple yet follows a pattern that doesn’t match ordinary plurals. In writing, especially in academic and business contexts, using the correct form matters. Getting it wrong can weaken your credibility, so let’s explore this word deeply and make sure you never hesitate again.

The plural of basis is bases, and this small detail has created confusion for learners for centuries. When you say the singular, it sounds like bay-sis, but the plural sounds like bay-seez. That change in sound makes it trickier than regular plurals like book/books or car/cars. To master it, you need to understand the history of the word, the grammar rules behind it, and how other similar words behave.

Common Academic Words

Singular	Plural	Meaning	Example
Basis	Bases	Foundation or starting point	The bases of the plan were strong.
Thesis	Theses	Research paper or idea	She defended two theses last year.
Crisis	Crises	Time of great difficulty	The country faced several crises in 2020.
Analysis	Analyses	Detailed examination	The scientist performed many analyses.
Hypothesis	Hypotheses	Proposed explanation	They tested several hypotheses.
Diagnosis	Diagnoses	Identification of disease	The doctor made quick diagnoses.
Prognosis	Prognoses	Forecast of outcome	Different prognoses were considered.
Synopsis	Synopses	Summary of text	Students wrote short synopses.
Axis	Axes	Central line	The graph has two axes.
Parenthesis	Parentheses	Curved punctuation marks	Use parentheses to explain details.

Science and Medicine

Singular	Plural	Meaning	Example
Metastasis	Metastases	Spread of cancer	The patient had lung metastases.
Epiphysis	Epiphyses	Bone end part	Growth occurs at the epiphyses.
Diaphysis	Diaphyses	Shaft of bone	The diaphyses are long and strong.
Symphysis	Symphyses	Joint between bones	The pelvis has two symphyses.
Psychosis	Psychoses	Severe mental disorders	Doctors treated several psychoses.
Neurosis	Neuroses	Anxiety disorders	Stress leads to different neuroses.
Tuberculosis	Tuberculoses	Bacterial lung infections	Ancient records mention tuberculosis.
Sclerosis	Scleroses	Hardening of tissue	Different scleroses affect nerves.
Hematosis	Hematoses	Formation of blood	Scientists studied hematoses.
Necrosis	Necroses	Death of cells	The tissue showed several necroses.

Linguistics and Grammar

Singular	Plural	Meaning	Example
Ellipsis	Ellipses	Omission of words	Writers use ellipses for suspense.
Emphasis	Emphases	Special importance	Different emphases improve speeches.
Synopsis	Synopses	Summaries of texts	Teachers requested synopses.
Antithesis	Antitheses	Direct opposites	Light and dark are antitheses.
Hypostasis	Hypostases	Essence or underlying reality	Philosophers debated several hypostases.
Paralysis	Paralyses	Loss of movement	Injuries caused multiple paralyses.
Aposiopesis	Aposiopeses	Sudden breaking of speech	Writers used dramatic aposiopeses.
Tmesis	Tmeses	Word separation in speech	Ancient poetry has tenses.
Chresis	Chreses	Use of words	Different chreses appear in texts.
Prosopopoeia (rare -is form)	Prosopopoeiae	Personification	Old rhetoric had prosopopoeiae.

Philosophy and Logic

Singular	Plural	Meaning	Example
Hypothesis	Hypotheses	Assumed explanation	The theory rests on three hypotheses.
Thesis	Theses	Argument or idea	Students debated two theses.
Antithesis	Antitheses	Opposite ideas	The antitheses challenged tradition.
Synthesis	Syntheses	Combination of ideas	Philosophers proposed new syntheses.
Apothesis	Apotheses	Divine elevation	Ancient myths tell of apotheses.
Hypostasis	Hypostases	Underlying realities	Scholars studied divine hypostases.
Catharsis	Catharses	Emotional release	Plays offered many catharses.
Metaphysis	Metaphyses	Part of bone (metaphorically used)	Thinkers compared minds to metaphyses.
Crisis	Crises	Turning points	Ideas reached new crises.
Gnosis	Gnoses	Spiritual knowledge	Teachers shared hidden gnoses.

Biology and Anatomy

Singular	Plural	Meaning	Example
Oasis	Oases	Fertile spot in desert	Caravans rested at the oases.
Prognosis	Prognoses	Expected outcome	Doctors gave hopeful prognoses.
Stasis	Stases	State of balance	Scientists studied fluid stases.
Metamorphosis	Metamorphoses	Transformation in form	Caterpillars undergo many metamorphoses.
Apoptosis	Apoptoses	Cell death	The body controls apoptoses.
Cytosis	Cytoses	Cell processes	Biology covers different cytoses.
Osmosis	Osmoses	Fluid movement through membrane	Plants rely on osmoses.
Fibrosis	Fibroses	Formation of excess tissue	The patient had lung fibroses.
Dermatosis	Dermatoses	Skin diseases	Doctors treated rare dermatoses.
Psychosis	Psychoses	Severe mental illness	Many patients suffered psychoses.

Literature and Rhetoric

Singular	Plural	Meaning	Example
Aposiopesis	Aposiopeses	Sudden speech break	His anger caused aposiopeses.
Chiasmus	Chiasmi/Chiasmuses	Rhetorical reversal	Speeches used clever chiasmi.
Paralysis	Paralyses	Figurative immobility	Fear caused emotional paralysis.
Emphasis	Emphases	Stress on words	Writers placed strong emphasis.
Ellipsis	Ellipses	Omission of text	Authors wrote with many ellipses.
Antithesis	Antitheses	Direct opposites	Good and evil are antitheses.
Hypothesis	Hypotheses	Assumed explanation	Scholars tested bold hypotheses.
Synthesis	Syntheses	Combination of ideas	New syntheses shaped thought.
Paradosis	Paradoses	Transmission of texts	Ancient scribes managed paradoses.
Mimesis	Mimeses	Imitation in art	Plays reflect cultural mimeses.

Religion and Theology

Singular	Plural	Meaning	Example
Hypostasis	Hypostases	Divine persons	The Trinity has three hypostases.
Gnosis	Gnoses	Spiritual knowledge	Mystics sought hidden gnoses.
Anamnesis	Anamneses	Religious remembrance	Rituals include anamneses.
Parousia	Parousiae	Second comings	Theologians discussed multiple parousiae.
Exodus	Exoduses	Mass departures	History tells of great exoduses.
Genesis	Geneses	Origins or beginnings	Many myths explain cosmic geneses.
Apothesis	Apotheses	Elevation to divine	Ancient gods experienced apotheses.
Metanoia (rare -is root)	Metanoiae	Spiritual repentance	Preachers stressed metanoiae.
Charis	Chares/Charises	Divine grace	The Bible speaks of God’s chares.
Crisis	Crises	Spiritual turning points	Faith communities faced many crises.

Law and Politics

Singular	Plural	Meaning	Example
Crisis	Crises	Political turning points	Nations face global crises.
Thesis	Theses	Legal arguments	Lawyers presented new theses.
Hypothesis	Hypotheses	Assumptions in law	Courts tested possible hypotheses.
Analysis	Analyses	Case breakdowns	Legal experts wrote sharp analyses.
Diagnosis	Diagnoses	Identifications of crime	Reports contained accurate diagnoses.
Prognosis	Prognoses	Predictions in cases	Judges made balanced prognoses.
Axis	Axes	Central alliances	Powers formed new axes.
Emphasis	Emphases	Stressed arguments	Lawyers placed strong emphasis.
Paralysis	Paralyses	Political stagnation	Governments suffered policy paralysis.
Antithesis	Antitheses	Contradictory laws	Reforms opposed old antitheses.

Geography and Environment

Singular	Plural	Meaning	Example
Oasis	Oases	Fertile desert area	Travelers found water at the oases.
Axis	Axes	Central lines of Earth	Earth spins on its two axes.
Crisis	Crises	Environmental disasters	The world faces climate crises.
Hypothesis	Hypotheses	Theories in geography	Geographers tested climate hypotheses.
Analysis	Analyses	Study of data	Experts carried out soil analyses.
Prognosis	Prognoses	Predictions about future	Scientists made alarming prognoses.
Paralysis	Paralyses	Inactivity in action	Policy paralysis slowed climate change efforts.
Stasis	Stases	States of balance	Rivers remained in natural stasis.
Metamorphosis	Metamorphoses	Transformations in nature	Butterflies undergo striking metamorphoses.
Necrosis	Necroses	Death of organisms	Forests showed signs of tree necroses.

Mathematics and Geometry

Singular	Plural	Meaning	Example
Axis	Axes	Reference lines in math	Graphs rely on the axes.
Hypothesis	Hypotheses	Assumptions in math	Proofs begin with logical hypotheses.
Analysis	Analyses	Study of numbers	Mathematicians performed deep analyses.
Synthesis	Syntheses	Combination of ideas	New formulas emerged from syntheses.
Thesis	Theses	Mathematical arguments	Scholars wrote their math theses.
Crisis	Crises	Turning points in theory	The field faced intellectual crises.
Paralysis	Paralyses	Stagnation of work	Projects stalled due to funding paralyses.
Prognosis	Prognoses	Predictions in data	Analysts gave cautious prognoses.
Basis	Bases	Foundations of math	Algebra rests on firm bases.
Hypostasis	Hypostases	Underlying principles	Geometry explains hidden hypostases.

Psychology and Sociology

Singular	Plural	Meaning	Example
Psychosis	Psychoses	Severe disorders	Doctors treated many psychoses.
Neurosis	Neuroses	Anxiety-related illness	Stress causes different neuroses.
Catharsis	Catharses	Emotional release	Art brought needed catharses.
Crisis	Crises	Turning points in life	People face personal crises.
Hypothesis	Hypotheses	Theories of behavior	Psychologists tested new hypotheses.
Paralysis	Paralyses	Social inaction	Society struggles with policy paralysis.
Basis	Bases	Underlying reasons	Trust forms the bases of relationships.
Stasis	Stases	Lack of change	Communities entered cultural states.
Gnosis	Gnoses	Knowledge or insight	Thinkers sought spiritual gnoses.
Emphasis	Emphases	Stressed ideas	Teachers placed strong emphasis.

History and Culture

Singular	Plural	Meaning	Example
Genesis	Geneses	Origins or beginnings	Myths tell of cosmic geneses.
Exodus	Exoduses	Mass departures	History records great exoduses.
Crisis	Crises	Turning points	Wars caused severe crises.
Thesis	Theses	Statements of thought	Philosophers wrote many theses.
Antithesis	Antitheses	Opposites in culture	Revolutions formed cultural antitheses.
Hypothesis	Hypotheses	Historical theories	Historians debated bold hypotheses.
Analysis	Analyses	Detailed studies	Archives allow deep analyses.
Synthesis	Syntheses	Cultural combinations	Traditions merged in creative syntheses.
Prognosis	Prognoses	Predictions of events	Leaders made future prognoses.
Basis	Bases	Foundations of history	Empires rested on fragile bases.

Technology and Computing

Singular	Plural	Meaning	Example
Analysis	Analyses	Study of data	AI systems run complex analyses.
Hypothesis	Hypotheses	Tested assumptions	Engineers worked on coding hypotheses.
Axis	Axes	Reference lines	3D models require axes.
Basis	Bases	Core structures	Algorithms form the bases of AI.
Crisis	Crises	Failures or breakdowns	Tech firms faced data crises.
Synthesis	Syntheses	New creations	Developers built fresh syntheses.
Thesis	Theses	Research works	Students submitted computing theses.
Prognosis	Prognoses	Future outlooks	Experts gave positive prognoses.
Emphasis	Emphases	Stress on features	The design had user emphases.
Stasis	Stases	No progress	Projects stalled in digital stages.

Mixed Words (General Use)

Singular	Plural	Meaning	Example
Basis	Bases	Foundations	Success rests on solid bases.
Crisis	Crises	Difficult times	Families faced financial crises.
Thesis	Theses	Papers or ideas	Scholars defended long theses.
Hypothesis	Hypotheses	Assumptions	Experiments test bold hypotheses.
Analysis	Analyses	Studies	Reports provided detailed analyses.
Synthesis	Syntheses	Combinations	Cultures create new syntheses.
Diagnosis	Diagnoses	Identifications	Doctors gave accurate diagnoses.
Prognosis	Prognoses	Predictions	Leaders offered cautious prognoses.
Emphasis	Emphases	Stressed points	Teachers used clear emphases.
Oasis	Oases	Fertile places	Camels drank at desert oases.

Conclusion

Mastering the plural of basis gives you an advantage in writing. It’s a word that appears often in education, research, and even everyday discussions. Using bases correctly shows your attention to detail and respect for language rules. Beyond grammar, it builds clarity and ensures your message is understood without distraction.

The next time you face a word ending in -sis, remember this rule and apply it confidently. By recognizing patterns, using examples, and learning synonyms, you can avoid errors and write with confidence. The plural of basis may puzzle learners at first, but with practice, it becomes second nature.