x is equal to unity
("unity" has to do with a "unit", i.e. 1, not "the state of being joined together or in agreement".)
You are using
...in their sense as mathematical jargon to mean 1.0. They are synonymous.
"Unit" or "unity" are used in this way when values are scaled so that their sum equals 1.0.
Doing so makes "general" calculations easier.
One would not say
equal to the unit
equal to the 1.0
since "unit" is representational shorthand for a number.