Irregular Plural nouns

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Across
  1. 2. a word, clause, or sentence inserted as an explanation
  2. 4. a succulent plant with a thick, fleshy stem that typically bears spines
  3. 7. a group of living organisms consisting of similar individuals capable of exchanging genes
  4. 8. either of two small wingless parasitic insects that live on the skin of mammals and birds
Down
  1. 1. any of a group of spore-producing organisms feeding on organic matter
  2. 3. detailed examination of the elements or structure of something
  3. 5. microscopic living organisms, usually one-celled, that can be found everywhere
  4. 6. a principle or standard by which something may be judged or decided