posted by Anonymous .
Is it correct to say "A deterioration in my grandfather's health and memory has just begun"?. Or is it began?
Begun is correct. Began is past tense. Begun this the past participle, so "has begun" is correct. :)
"I Have Not Yet Begun to Fight," 1779 John Paul Jones http://www.eyewitnesstohistory.com/johnpauljones.htm
"We Have Only Just Begun to Fight". Franklin Roosevelt. October 31, 1936. https://patriotpost.us/documents/284