A. Some words, however, remain the same for plural.
- deer – deer
- sheep – sheep
- salmon – salmon
- mackerel – mackerel
B. An “a” ending
- phenomenon – phenomena
- criterion – criteria
C. A change from um to a
- curriculum – curricula
- medium – media
- memorandum – memoranda
D. A change of end letters to es or i for foreign words that have become part of English.
- Virus – viruses
- octopus – octopuses
- circus – circuses
- stimulus – stimuli
- syllabus – syllabuses or syllabi
- terminus – terminuses or termini
