phenomenon?

A rainbow is one,on the other hand so is a ghost sighting.

I do not have a speech topic but that is what the word means.

phe·nom·e·non (f-nm-nn, -nn) KEY

NOUN:

pl. phe·nom·e·na (-n) KEY

An occurrence, circumstance, or fact that is perceptible by the senses.

pl. phe·nom·e·nons

An unusual, significant, or unaccountable fact or occurrence; a marvel.

A remarkable or outstanding person; a paragon. See Synonyms at wonder.

Philosophy In the philosophy of Kant, an object as it is perceived by the senses, as opposed to a noumenon.

Physics An observable event.

1. An occurrence, circumstance, or fact that is perceptible by the senses.

2. An unusual, significant, or unaccountable fact or occurrence; a marvel.

Have you ever walked into a room you have never been in before and the smell in the room instantly reminded you of a time and place in your past ? Might make for a interesting speech !