One of my most vivid memories from law school (nightmares?) always happened on the first day of classes. Because of my library background, I got a job working in the law library three months before classes began for my first year of school and during the course of my years at school, I could watch each new class. Added to this, my father was an attorney and I had a passing acquaintanceship with at least the sound of legal terminology. Right after the first class in property law, there was always a mad dash to the library focused entirely on the law dictionaries. To almost every student, law was a foreign language that needed to be translated into something resembling English. I was working at the reference desk in the library and remember laughing as the entire first year class congregated around the dictionary shelves.
Genealogists have the same problem in deciphering legal documents but usually without the benefit of the law library or the library's reference section. But any library with even a modest reference section will very likely have the ultimate reference book of legal terminology; Black's Law Dictionary. What is even more convenient, this venerable reference book is mostly available in digital format. I say "mostly" because there are so many editions of this book, that it would be difficult to review all of them. The first edition was compiled in 1891. The latest edition, variously termed the 9th, 12th or even the 15th edition, was published in 2009. The book is also available in pocket editions, paperback, hardbound and iPhone app.
Garner, Bryan A., and Henry Campbell Black. Black's Law Dictionary. St. Paul, Minn: Thomson West, 2009.
If you haven't ever referred to Black's Law Dictionary, it is likely that you haven't reached that stage of your genealogical investigations that takes you into original deeds, wills, probate files and litigation. One of the most remarkable things about the legal profession as a whole is the absolute conservative nature of legal jargon. When I draft a will today, I use some of the same language contained in wills over 500 years old and it is not unusual for me to throw in a few Latin phrases when I write legal briefs.
Even though I mention (and recommend) Black's Law Dictionary to any researcher involved in legal documents, I do have make the qualification that the entries in the Dictionary sometimes need a dictionary to understand the definition. Now, with the Internet, I only very rarely resort to a printed paper edition of any law book, even Black's Law Dictionary, and I haven't been in a law library (except to use the restroom) in years. I do have a paper copy of one of the editions sitting by my desk however. Here is an example of the definition of the word seisen from an online source:
seisin (sees-in) n. an old feudal term for
having both possession and title of real property. The word is found in
some old deeds, meaning ownership in fee simple (full title to real
property). (See: fee simple, seized) From The Free Dictionary by Farlex.
Well, that is not really the full meaning of the term. You have to a go a lot further into the history of land ownership before you begin to understand what was meant to be seized of a piece of property. In the earliest times of English law, part of the process of conveying real property consisted of handing an actual handful of the dirt to the new owner, who was then said to be seized of the property. If you keep following the terms, you can spend a long time learning before you grasp the entire concept conveyed by one term.
What about online resources other than Black's Law Dictionary? If you use Google, you can always look up a word's definition by typing "define [word]." This search form will produce references to multiple dictionaries.
One rule about law is absolutely essential to understanding any legal document, old or new, that is, do not assume a common meaning of any of the words used. Even terms that might seem familiar to you may have a strict legal meaning in the context of a legal document. After all, there has to be some reason to pay attorneys all that money.