Over the centuries many millions of people have left England, Ireland, Scotland & Wales and made their homes overseas.
Reasons vary. Some fled religious and/or political persecution. For others, harvests failed and to stay at home meant starvation. Some were criminals, sentenced to deportation, and many orphaned children found themselves far from home as part of Child Migration Schemes. For yet others, the lure of a better life, or to join family members, was the attraction.
If you have gaps in your tree - maybe a family is in one census, but there's no trace of them in the next, or perhaps you have a birth, then nothing more - a glance at the dates above, and some intelligent guesswork may provide you with clues as to where to begin your search.
Between 1820 and 1920, over 30 million immigrants arrived in America, by far the most popular destination, not just for emigrants from the UK, but all over the world.
Over 1,000,000 went to Australia (initially as convicts), and hundreds of thousands to Canada, New Zealand and South Africa.
There are many records of their movements, from leaving the Uk, and beyond - passenger lists, ships manifests, naturalization records, land deeds, census records, military records, criminal records - just some of the sources from which you might find details of your ancestors.
If there are no family stories about what might have happened to them, delving some of the above records may find some of them for you.
It is possible to try a global search on Ancestry.com (you don't have to be a member to search), for a short-cut way of finding lost relatives.
I had an ancestor for whom I only had a birth record, and no more, and I made the assumption (a lesson I learned - don't ever assume anything) that she must have died in childhood, and left her alone, attempting the occasional search through bmd records.
One day I did a global search on Ancestry, hoping to find a death entry, and was shocked to see her name associated to a New York passenger list. My heart racing, I took a trial membership, checked the entry, and found it was definitely her, travelling as the fiancee of an American serviceman, her reason for travelling being to marry, and settle in Philadelphia.
It had never occurred to me that she might have emigrated.
The entry confirmed her home address in the UK, so I knew I had the correct relative. I was overjoyed, as I had been trying to trace her for over two years.
For me, the subscription to Ancestry paid for itself there and then, and I have gone on to find other family members too. The ability to search multiple databases at one time is priceless.