The 72-year-old "Piku" star wrote on his blog that his mother's birthday was "an auspicious day" for him and recalled how he used to address her.
"For long, in my early years I addressed her as Amma ji, then it became Amma, then Maa... And now Maa ji, if I need to have reference to her in conversation...
"But honestly I loved Amma ji... There was a bit of the ground the earth where I was born, Allahabad, in that address...," he wrote.
Bachchan said even though the numbers of letters in her calling diminished, the respect remained.
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The "Paa" actor said he has been asked often why he talks about his father more than his mother.
"Many question me on why I never say much about my Mother... Always talking only about my Father...
"How does one answer that... Can anyone have a justifiable answer to describe Mother... Or what she means to us all... Improbable, absolutely improbable to put in words in whatever language it be, to express MOTHER...," he said.
"I send my gracious thanks to all that send me greetings for my Mother's birthday Aug 12...