Different spellings of 'Prasaad' in Gurbani...

 
In Gurbani, the word "Prasaad" is spelt in 3 ways: (1) ਪ੍ਰਸਾਦੁ - prasaad(u); (2) ਪ੍ਰਸਾਦਿ - prasaad(i); and (3) ਪ੍ਰਸਾਦ - prasaad. Depending on the spelling, the word can mean different things:

(1) ਪ੍ਰਸਾਦੁ - prasaad(u) = blessing; grace
Example:

ਨਾਨਕ ਪ੍ਰਭ ਸਰਣਾਗਤੀ ਕਰਿ ਪ੍ਰਸਾਦੁ ਗੁਰਦੇਵ ॥੧॥"Nanak seeks the Sanctuary of God; please bless me with Your Grace, O Divine Guru. ||1||"
(Gauree M:5, Ang 269)

(2) ਪ੍ਰਸਾਦਿ - prasaad(i) = through the blessing; by the grace of
Example:

ਜਿਹ ਪ੍ਰਸਾਦਿ ਛਤੀਹ ਅੰਮ੍ਰਿਤ ਖਾਹਿ ॥ ਤਿਸੁ ਠਾਕੁਰ ਕਉ ਰਖੁ ਮਨ ਮਾਹਿ ॥
"By His Grace, you partake of the thirty-six delicacies; enshrine that Lord and Master within your mind."
(Gauree M:5, Ang 269)

(3) ਪ੍ਰਸਾਦ - prasaad = when used as preposition 
Example:

ਗੁਰੁ ਪੂਰਾ ਪੂਰਾ ਪਰਸਾਦ ॥੨॥      
"Perfect is the Grace of the Perfect Guru. ||2||"
(Bhairo M:5, Ang 1143)