- By adding –s if there is a vowel before the -y
- By changing –y into –ies if a noun ends in a consonant before the -y.
Singular | Plural |
analysis | analyses |
axis | axes |
basis | bases |
crisis | crises |
diagnosis | diagnoses |
ellipsis | ellipses |
hypothesis | hypotheses |
oasis | oases |
parenthesis | parentheses |
thesis | theses |