Inseparable (adjective)

Unable to be separated or divided.

Origin:

From in- (not) + separable (able to be separated).

Examples:

1. The two are inseparable friends.
2. The couple were inseparable, always seen together.
3. The two parts of the machinery were inseparable.
4. The two brothers were inseparable in childhood but grew apart as adults.
5. The inseparable bond between mother and child.