Both are fine, but in written form throw a comma after "closing" and "conclusion".

Student or Learner
"In closing we petition for the approval of...."
"In conclusion we petition for the approval of...."
Is there a difference between "in closing" and "in conlusion"? Are both possible in the above construction?
Thanks.
Both are fine, but in written form throw a comma after "closing" and "conclusion".
I think there is a difference.
In closing - you are bringing your words/speech to an end by writing/saying something that does not necessarily link to what went before. 'In closing, I would like to say a few words of gratitude to my new father-in-law ...'
In conclusion - you are summing up what went before, often by bringing the different strands of your thoughts or reasoning together into one neat summary. If opinions A, B and C are stated in their respective paragraphs, the final paragaph D - the conclusion - will bring together all these opinions, thereby giving the overall argument more force.
The other meaning of conclude (apart from summing up) is to 'close'. They mean the same thing in the context.
not a teacher