The English language phrases Ipso Facto and De Facto have related meanings, but they are different as I shall explain, with examples of their British English usage.
Ipso Facto means "by the fact itself" - i.e. something that is immediately known from an initial fact.
"I am English, ipso facto British". This is because all English people are British.
"Faustus had signed his life away, and was, ipso facto, incapable of repentance."
"The school does not provide scholarships, ipso facto the children's parents are rich."
De Facto means something that exists in reality, but which is not officially recognized by law.
"English is the de facto language of Great Britain." There is no law that says English is the official language of the UK, but everyone knows it is.
"She is my de facto wife, even though we have not been married." In Australia and New Zealand, people who live together as husband and wife are treated as if they are married, even though they are not.
De Facto is the opposite of De Jure, which refers to legally recognized practices, whether or not they actually take place.
Please note that neither phrase is commonly used in British English language outside of some academic or legal communities.
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