Truth, realness, virtue, honesty, sincerity.
Satya is one of the five virtues for the first leg of the way of the Rajayoga.
When in your heart of hearts an impuls builds, which then appears in utterable expression, one may consider such an impulse as a manifestation of the truth. This inner truth appears when a human is sincere, also towards the self.
A live without truth becomes a hideout full of misery and strife.
There is nothing greater then the truth, nothing more durable. Truth is the all-protecting god.
See also
Hum,
Sacha and
Sat.