it often serves to illustrate the state of your emotion

Felis Catus is your taxonomic nomenclature -
An endothermic quadruped, carnivorous by nature.
Visual, olfactory, and auditory senses
contribute to your hunting skills, and natural defenses.
I find myself intrigued by your subvocal oscillations -
A singular development of cat communications
that obviates your basic hedonistic predilection
for a rhythmic stroking of your fur, to demonstrate affection.
A tail is quite essential for your acrobatic talents -
You would not be so agile if you lacked its counter-balance.
And when not being utilized to aid in locomotion,
it often serves to illustrate the state of your emotion.
Oh Spot, the complex levels of behavior you display
connote a fairly well-developed cognitive array.
And though you are not sentient, Spot, and do not comprehend,
I nonetheless consider you a true and valued friend.
[Star Trek: The Next Generation. Data (Brent Spiner): 'Ode to Spot']