The plural of the word diagnosis is: diagnoses. diagnos. diagnostic. diagnosese. diagnose.

diagnoses.

The key concept here is understanding how to form the plural of nouns in English, particularly for words that end in -is. The correct plural form of "diagnosis" is "diagnoses," which follows the rule of changing -is to -es for pluralization.

Here are further explanations.

• Option A: This is the correct plural form, as it appropriately changes the ending from -is to -es.

• Option B: This option is incorrect because "diagnos" does not follow the standard pluralization rules and is not a recognized word.

• Option C: This option refers to an adjective rather than a noun, making it irrelevant in the context of pluralization.

• Option D: This option is a misspelling and does not represent a valid word.

• Option E: This is the base form of the word and does not indicate a plural form.