Gayatri Mantra

Om
Bhur Bhuva Svaha
Tat Savitur Varenyam
Bhargo Devasya Dheemahi
Dhiyo yonah Prachodayat

(Om) Om (Dheemahi) We meditate (Bhargo) upon the spiritual Effulgence (Varenyam Devasya) of THAT Adorable supreme Divine Reality (Savitur) the Source (Bhur, Bhuva, Svaha) of the physical, the Astral and the Heavenly Spheres of Existence. (Tat) may THAT Supreme Divine Being (Prachodayat) enlighten (Yo) which (Nah) our (Dhiyo) Intellect (so that we may realise the Supreme Truth).

What is "Sampoorna Gayatri"?

Om : This is Pranava

Bhur, Bhuva, Svaha : The Mahavyahritis relating to Gayatri Mantra.

The conventional Mahavyahritis pronounced before commencing any spiritual ceremony are as follows:

OM BHUH OM BHUVAH OM SUVAH

OM MAHAH OM JANAH OM TAPAH

OM SATYAM

These are the Seven spheres of existence beginning with the physical (BHUH).

Actual Gayatri Mantra:

TAT SAVITUR VARENYAM

BHARGO DEVASYA DHEEMAHI

DHIYO YONAH PRACHODAYAT

These three aspects taken together form 'Sampoorna Gayatri'.