Unbound

When a book is covered in cloth of a good dark tint it may be allowed to remain unbound, but the primrose and lilac hues soon call out for the aid of the binder.

Near-synonyms: unconstrained, unrestrained, unencumbered; unfettered, fetterless

The terms of the contract inadvertently left certain unbound aspects to subjective interpretation.

Near-synonyms: unfettered, fetterless, unrestrained, unchained, unshackled, shackleless, unmanacled, unhandcuffed

The hostages' hands were left unbound.

an unbound book

Beneath an old ebony table were two long carved oak chests. I lifted the lid of one, and at the top was a once-white surplice covered with dust, and beneath was a mass of tracts — Commonwealth Quartos, unbound — a prey to worms and decay.

Helium-2 is unbound, as it is energetically favorable for it to split into two separate protons.