simultaneous operation vs parallel operation

simultaneous operation and parallel operation both are nouns.

Word	Noun	Adjective	Verb	Adverb
simultaneous operation	Yes	No	No	No
parallel operation	Yes	No	No	No

As nouns, simultaneous operation and parallel operation are synonyms defined as:

simultaneous operation and parallel operation: the simultaneous execution of two or more operations

simultaneous operation (noun)	parallel operation (noun)
the simultaneous execution of two or more operations	the simultaneous execution of two or more operations