The symbol AH is multivalent, which means it has many meanings.

AH is sometimes refered to as a union of OM AH and HUM. A three-in-one. Our relative existence is seen as a threefold of body, speech, and mind. Buddhists speak of a transformation of our impure body speech and mind into a pure body speech and mind. In this context Ah is the union of all three. The AH seen as one of the three, it represents the speech aspect. This is why in some practices it is visualized at the throat.

It can represent the shortest version of the Prajanparamita sutras (sacred writings).These sutras are found in various lengths. There is one with 100,000 lines, one with 25,000 lines, 1,000 lines etc. The shortest version is said to be contained in the one syllable "AH". The Perfection of Wisdom Sutras (in English), teach the meaning of emptiness explicitly and the paths to Buddhahood implicitly. Both of these topics basically contain the scope of the Buddhist path. The term paths here mean consiousnesses that need to be generated.

Buddhism is a system that offers ways to change bad habits into good habits. Good here meanining thoughts and actions that benefit all.

In yet another context we can read that, " In the Vimalaprabha commentary on Kalachakratantra the state of supreme ,indestructible bliss is identified with the syllable "A",which as the first syllable of the Sanskrit alphabet, stands for the dharma-source and for the vajra-womb of all the Buddhas. As such, it is seen as the fundamental cause of all expressions, as the birthplace of all mantras. In light of this view, the individual syllables that constitute a tantric discourse are declared to be of the nature of a mantra; and the mantra is said to be in the body. Thus, a tantra, which is identified with mantra on this ground, is a text that is encoded in the individual's body in the form of mantric syllables." Vesna Wallace, From As Long as Space Endures.

The syllable AH is also used in a practice called " dream yoga". It is vizualised before you go to sleep. Yogi's use sleep time for practice as well! Tantric practice is very economic in this way. It uses all of our experiences.

Ah expresses an open state. One of infinite possibility.