The ending –is is changed to –es
| Singular | Plural |
|---|---|
| analysis | analyses |
| axis | axes |
| basis | bases |
| crisis | crises |
| diagnosis | diagnoses |
| ellipsis | ellipses |
| hypothesis | hypotheses |
| oasis | oases |
| parenthesis | parentheses |
| thesis | theses |
| Singular | Plural |
|---|---|
| analysis | analyses |
| axis | axes |
| basis | bases |
| crisis | crises |
| diagnosis | diagnoses |
| ellipsis | ellipses |
| hypothesis | hypotheses |
| oasis | oases |
| parenthesis | parentheses |
| thesis | theses |