Feminine of a trillionth.
It is a fractional that corresponds to a part in a trillion of fractions.
TRILLIONTH, A portion that corresponds to 1/1. 000. 000. 000. 000. 000. 000 or 1 / 10 ^ 18 parts of the unit. In the English system corresponds to 1/1. 000. 000. 000. 000 or 1/10 ^ 6 the unit's parts