Not only does my ex-husband have no biological link to Irina - neither do I.

BBC: Switched at birth, then meeting aged 12

But because this is not a romantic or biological link, there is always a chance of this changing and I am well aware of it.

FORBES: What Is It Like To Be A Single Father?

Other biological processes also link seemingly unrelated diseases.

WSJ: Genes May Link Disparate Diseases

UNESCO, through its Local and Indigenous Knowledge Systems (LINKS) Programme, is working to bring recognition to this issue, and to demonstrate the link between cultural and biological diversity.

UNESCO: Indigenous Peoples

When we report on stories such as that one, we take for granted the idea that peoples' bodies can be identified with certainty, not just by their clothing or by their fingerprints, but by their DNA. We can also link criminals to victims or to evidence and we can link people to their biological relatives.

NPR: Pioneering DNA Forensics

Because the link between people and plants is so fundamental to the conservation of both biological and cultural diversity, it concentrates on the core of our capacity building: training in applied ethnobotany, providing people with inter-disciplinary skills highly relevant to conservation action.

UNESCO: Natural Sciences