Trillionth (adjective)

1. Relating to or denoting the billionth part of a trillion; one of a trillion equal parts.
2. Very small in amount or degree.

Origin:

From the noun trillion + -th, the adjective is formed by taking the ordinal form of the noun.

Examples:

1. The trillionth part of a second is a very small interval of time.
2. The trillionth part of a dollar is a very small amount of money.
3. He was just a trillionth of a second late in pressing the button.
4. The trillionth of a gram is a very small quantity of weight.
5. A trillionth of a inch is a very small unit of measure.