The old, in time, cap formative period of mathematics (7,5)
I believe the answer is:
decimal point
'period of mathematics' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'the old in time cap formative' is the wordplay.
'old in time cap' can be anagrammed to 'DECIMAL POINT'.
But, I am not sure how this is indicated.
Can you help me to learn more?
(Other definitions for decimal point that I've seen before include "Dot in a number" , "Dot between figures" , "I'm dot in place (anag)" , "The dot in 10.67" , "What is in the middle of 1.5 and 2.5, say" .)