Is there a word or expression for people who have lived at the same time, even if other was only during one day? I mean people who have had at least a theoretical chance of meeting and interacting with each other at least once during their lifetime. I'm aware of the word "contemporary", but as far I have understood, it usually refers to eg. two persons whose dates of birth and/or death are quite close to the ones of the other person, so that being born one day before other person's death is not sufficient. What word or expression do you recommend?
Contemporary is the word to use. From OED:
a. Belonging to the same time, age, or period; living, existing, or occurring together in time.
Having existed or lived from the same date, equal in age, coeval.
- Occurring at the same moment of time, or during the same period; occupying the same definite period; contemporaneous, simultaneous.
However, because it does imply a certain looseness, you may be able to imply a more exact relationship by using contemporaneous.
- a. Belonging to the same time or period; existing or occurring at the same time. Const. with. b. Covering the same space of time.
- Originated at the same time or during the same historical or geological period; of the same age.
The meanings of contemporary and contemporaneous overlap, but dictionaries aren't particularly good at conveying nuances of meaning. I would certainly give contemporaneous less leeway in matching dates than I would hearing the word contemporary.
It would probably work to say that the people were alive simultaneously (at the exact same time) but this is usually used of discrete events occurring at the same moment, rather than overlapping periods of time. However, this is likely to be the only word which definitely means the people were alive at the exact same time, rather than simply in the same period.
Coexist - exist at the same time and/or in the same place.