Some nouns end in ‘f’ or ‘fe’. They make their plurals by changing ‘f’ or ‘fe’ into ‘ves’.

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Across
  1. 2. handkerchief
  2. 4. half
  3. 6. wolf
  4. 7. ourself
  5. 9. calf
  6. 10. life
Down
  1. 1. thief
  2. 3. knife
  3. 5. loaf
  4. 8. leaf