The Trishula (trident) of Shiva is the symbol of the 3 qualities of Nature: the 3 Gunas and hence the 3 functions of Creator, Preserver and Destroyer.
The three prongs of the trishula also represent:
• The 3 personified Divinities of Creation, Sustenance and Dissolution (Brahma, Vishnu and Rudra) – The 3 Divinities depicted as separate entities in mythical stories are one and the same with Shiva. He alone creates, sustains and dissolves the universe.
• The 3 great universal acts of Creation, Sustenance and Dissolution – Shiva is the Master and Controller of all three universal acts.
• The 3 syllables of Omkara: A (akara), U (ukara) and M (makara) – The Omkara is the primal sound, the Word of God, which gave birth to entire universe. It is for this reason that Shiva is also called the Lord of Omkara (Omkareshvara).
• The 3 causes of the Universal Manifestation: Efficient, Instrumental and Material – All 3 causes originate and reside within Shiva, and there is no cause external to Him which brought about universal manifestation.
• The 3 Shaktis of Shiva – The power of Will (Iccha), the power of Knowledge (Jnana) and the power of Action (Kriya). It is through progressive expansion of these Shaktis that the Unmanifest impinges into universal experience.
• The 3 planes of reality that make up the manifest universe: Physical, Subtle and Causal – The multitudes of heavenly and hellish realms that make up the universe are all contained within these 3 planes of reality. Shiva alone is the Lord and Master over all planes and all realms of existence.
• The 3 qualities of Prakriti (primal nature): Sattva, Rajas and Tamas – All things in existence emerged by the admixture of these three primal qualities. Shiva is the supreme Purusha who is both Master over prakriti and the three qualities, yet beyond them at the same time.
• The 3 ordinary states of consciousness: Waking, Dreaming and Deep sleep. Shiva is ever existent within the 3 states, yet exists in the fourth transcendental state upon which the 3 ordinary states are founded.
• The triad impurities: Anava, Karma and Maya – which keep the individual being feeling that s/he is separate or separable from Shiva. Shiva is the Ruler over these three impurities, and alone by the descent of His grace can one work through these impurities to realize Him.
• The triadic essences: Pati, Pashu and Pasha – Which make up the trichotomy of existence. The trichotomy of all existence is held together within Shiva and in Him all three are realized as inseparable from one another.