New medical detail that determines numerical size (7,5)
I believe the answer is:
decimal point
'determines numerical size' is the definition.
I can't tell whether this defines the answer.
'new medical detail' is the wordplay.
'new' indicates anagramming the letters.
'detail' becomes 'point' (synonyms).
'medical' is an anagram of 'decimal'.
'decimal'+'point'='DECIMAL POINT'
'that' acts as a link.
Can you help me to learn more?
(Other definitions for decimal point that I've seen before include "The dot in 10.67" , "Dot between figures" , "Dot in a number" , "It separates pounds from pence" , "What is in the middle of 1.5 and 2.5, say" .)