Ipso facto is a Latin phrase, directly translated as by the fact itself. It is a term of art used in philosophy and law.

In law, this phrase is frequently employed to convey the idea that something which has been done contrary to law is void. For examp

"In propria persona" (Latin: "in one's own [proper] person"; often abbreviated "in pro per") describes someone who is representing himself or herself in a lawsuit rather than being represented by a lawyer. This term is used in California state courts, and

Quantum meruit is a Latin phrase meaning "as much as he has deserved". In the context of contract law, it means something along the lines of "reasonable value of services".

Wikipedia on Latin :)

A Man (plaintiff in this hypothetical) talks to a neighbor (defendant) and tells him he's going to build a wall on their property that will give a benefit to both the man and his neighbor. The neighbor neither agrees nor disagrees with what the man wants to build. The man builds the wall, and then asks the neighbor to compensate him for the benefit of the wall that he conferred on the neighbor (usually half the value of the wall). The neighbor refuses. The man is entitled to some compensation based on quantum meruit. This is because there was an implied promise between the man and the neighbor, which is derived from contract law, because the man was acting under the assumption that the neighbor would pay for part of his services. The plaintiff files suit in court on the basis of quantum meruit. The plaintiff makes an estimation of value conferred on the defendant, which the defendant has not paid. Plaintiff will likely win because of quantum meruit. The winning of the case will be directed as an assumpsit on a quantum meruit.