You'll Know Poem by Clive Blake

No mathematical formula
Can define love on a page,
No statistician can measure it,
There exists no such gauge.

Love cannot be ordered,
Nor can it be planned,
Not pulled out of a hat
By deft sleight of hand,
Impossible to touch,
But it can be felt,
It is best when it's shared
But it can't be dealt,
Invisible to all;
Gives no peacock show,
Has no shape, size, or form,
But yes - it can grow.

In spite of this -
When you're in love, be assured...
You'll know... you'll know.