Find the odd one out on the basis of singular and plural. Out of the given four nouns, three have the singular and plural alike except one. Identify the odd one:

The correct answer is "Ox"

Key Points

• Nouns that have the same singular and plural form are called "invariable nouns"
• "Sheep", "Deer", "Swine" are invariable nouns and their singular and plural form are the same.
• "Ox" is the only noun that is not alike in its singular and plural form. It is the only odd one out.
• The plural form of 'Ox' is 'Oxen' because some nouns adopt foreign rulings.
• The Foreign Plural nouns have irregular plural forms.
• They often make their plurals according to the rules of the language they were taken from (e.g. Latin or Greek or German).
• Sometimes there is more than one plural form possible or these forms have different meanings.

Thus, option 4 is the correct answer.