Shiva Purana
सूक्ष्ममेकाक्षरं विद्यात्स्थूलं पंचाक्षरं विदुः । सूक्ष्ममव्यक्तपंचार्णं सुव्यक्तार्णं तथेतरत् ९ ।
The subtle one is of a single syllable where the constituent five syllables are not differentiated clearly. The gross one is of five syllables where all the constituent syllables are manifest.
english translation
sUkSmamekAkSaraM vidyAtsthUlaM paMcAkSaraM viduH । sUkSmamavyaktapaMcArNaM suvyaktArNaM tathetarat 9 ।
hk transliteration by Sanscript