Root meaning: What is true, real, fact; the opposite of illusion.
ACIM: Transcendental reality or Heaven, beyond time and space, including all ideas inherent in reality. Only that is true, real, only that is Fact. All else is illusion. Truth was created by God. It is total, indivisible, all-inclusive, constant, changeless. It cannot be destroyed and when attacked it does not respond. It cannot be perceived, learned nor believed. It can only be known (see knowledge). It is given; truth is not up to you to establish. Truth is only joy and safety. The truth about you is grandeur, perfection. Yet you have feared truth and denied it (see denial), making illusions instead. Truth and illusions are mutually exclusive. To discover truth you must search out all that interferes with it (see T-14.VII.2:1). You must learn to distinguish between truth and illusion, letting illusions go without exception. Then “truth will dawn upon you of itself” (T-8.VI.9:11). See bringing darkness to light, illusions to truth. See W-pI.152.2-5.