conjoined, indivisible, inseparable, inseverable, intertwined...
no
separated
separated
The word you're thinking of is likely "inseparable," which means unable to be divided or separated. This term is commonly used in various contexts to describe things that are tightly connected or cannot be broken apart.
Solutions cannot be separated by sublimation.
Untouched. Unassailable.Incomparable.
An ensconced affix is a bound morpheme that cannot be further divided or separated from the base word it is attached to. This type of affix is firmly fixed in place within the word's structure and cannot stand alone as an independent word.
'a' is an idefinite artice but we cannot make another word from it.
A substance that cannot be separated physically is a pure substance.
An element cannot be separated into simpler substances by chemical means.
The mixture cannot be separated after it is baked.
Indispensible