31. Ovum- Ova
32. Ox- Oxen
33. Oasis- Oases
34. Parenthesis- Parentheses
35. Phenomenon- Phenomena
36. Radius- Radia
37. Synopsis- Synopses
38. Stratum- Strata
39. Symposium- Symposia
40. Stadium- Stadia/ Stadiums
41. Syllabus- Syllabi/ Syllabuses
42. Terminus- Termini
43. Tempo- Tempos
44. Thesis- Theses
45. Vertebra- Verbrae
46. Vertex- Vertices or Vertexes
47. Vortex- Vortexes or Vortices
48. Yo-yo- Yo-yoos
49. Yes- Yeses or Yesses
50. Zebra- Zebra or Zebra
