Refer to this extract from Act 1 Scene 1.

CURIO

     The hart.

ORSINO

Why, so I do, the noblest that I have.

Oh, when mine eyes did see Olivia first,

Methought she purged the air of pestilence.

20That instant was I turned into a hart,

And my desires, like fell and cruel hounds,

E'er since pursue me.

Curio mentions a ‘hart’ which is a male deer. However, Orsino refers to his noble ‘heart’. This is an example of a/an: