Ash generally refers to the Rowan tree (Sorbus aucuparia)—which is the tallest of all flowering plants—or the North American tree of the genus Fraxinus in the olive family.

The letter “Æ” is called ash and means “tree” in Old English.

Volcanic ash is low-density solidified rock material ejected from a volcanic vent into the air.

Yggdrasil in Norse Mythology is the "World Tree" —a gigantic ash. It holds all of the different worlds: Asgard, Midgard, Utgard and Hel. Its three roots dig to Hel, the sacred Well of Urd, and the spring of Mimir.

Ash (Shin Aleph) is the Hebrew word for fire.

Ash is another name for the Philosopher's Stone or the Stone of the Wise—an alchemical symbol of the transmutation of humanity's lower nature into a higher, more purified spiritual state.

Ash, or As, in Egyptian mythology was the hawk-god of the Sahara Desert.

Ash is a reminder of our mortality—on Ash Wednesday, when the priest uses his thumb to sign with the ashes on one's forehead, he says, “Remember, that thou art dust and unto dust thou shalt return.”