During the 1700s the terms Junior and Senior were often conveniences used by colonial families who lived in rural communities. These terms were used merely to distinguish between two person who lived in the same locality, had the same name, and were of different generations. Sometimes the men were related sometimes not; it was quite common in the Southern United States. These designations were usually not permanent either. For instance in a small town there may have been several men named John Anderson. They would have been given the designations Senior, Junior, First, and Second according to their ages to tell them apart from each other. If Peter Senior died or moved away it was quite common for the term to be dropped from his name. Then Peter Junior would become known as Peter Senior and all the other Peters would also change their designations to move up in the hierarchy.

As you research old letters, diaries, and wills you will encounter other terms for relationships whose meanings has changed over time, for instance, the term cousin. If the document is from Colonial times a good first guess would be that the term cousin meant a nephew or niece relationship. In fact the terms nephew and niece were not used as they are today to mean the son or daughter of a brother or sister until about the 1750s. Cousin was also used as we use it today to mean a child of one's aunt or uncle, but it was also often used to indicate almost any degree of relationship by blood or marriage -- except the relationships of the immediate family. As you may have noted one should not rely too heavily upon the terms of relationships in early genealogical documents. Conclusions about the relationships between people must be verified through other evidence.

Linguists say that the term nephew was derived from the Latin nepos meaning grandson. Likewise, the term niece was derived from the word neptis meaning granddaughter. Thus, in Middle English, the terms meant grandson and granddaughter. In the American Colonial period it is rare that the term nephew or niece was used to mean grandson or granddaughter. However, if the term nepos or neptis is used in a record they most certainly should be interpreted as meaning grandson and gran ddaughter. Generally nephew and niece have almost always carried the same meaning as they do today, that of the child of one's brother or sister. (When I looked up the term nephew in the Dictionary, I was surprised to find it also meant the illegitimate son of an ecclesiastic. In truth the dictionary put it more delicately by saying that the word nephew meant "a son of a celibate ecclesiastic.")

Another term which sometimes carried a different meaning prior to the 1750s was that of "in-law". The terms father-in-law, mother-in law, son-in-law, and daughter-in-law were frequently used to indicate the same relationship as they do today, a relationship by marriage rather than blood. However, the "in-law" term may also have referred to the relationships that we now call "step". In earlier times any relationship created by legal means, including step relationships, were often termed as "in-law". Thi s is particularly true in the cases of the terms daughter-in-law and son-in-law which often meant "stepchild", or father-in-law and mother-in-law which often meant "stepparent". The terms brother-in-law and sister-in-law more than likely carried the same meanings we give them today, that of a sibling's spouse.

And what about the terms brother and sister? It is not always possible to determine the relationship especially if you are reviewing a Puritan document of the mid 1600s. The term brother or sister could mean what it means today, a sibling with the same parents, or merely refer to a Brother in the church with no relationship at all. Even from the 1600s to the current day, some religions use the term Brother and Sister when referring to other members of their religion. In earlier times married couples r eferred to a brother-in-law or sister-in-law as just brother or sister. Some of the other obvious uses of brother or sister are in reference to a half-brother or sister or a stepbrother or sister. Once again the researcher should be cautious in attributing a blood relationship just from the mention of the terms brother or sister. Additional sources confirming the relationship should be sought. (Sister, of course, can also mean a Catholic Nun and Brother a member of a men's religious order.)

A few other terms to interpret with caution are:

Alias - Usually meant illegitimacy. The use of two surnames joined by Alias in early records were usually the surname of the reputed father and the surname of the mother. However, there were other cases when two names were joined in this way. Sometimes the name of the natural father, who had died, was joined to that of a stepfather. Or in the case of adoption the name of the natural father and the adoptive parent were sometimes used together.
Crazy - Only meant that the person was ill or in poor health and not necessarily that they were mentally ill.
Domestic - Used to mean a housewife. The term domestic now means a servant.
Housekeeper - Once meant property owner and could refer to a man or a woman.
Inmate - Did not always refer to a person in an institution. It may also mean someone who did not own the real estate on which he lived or a person living in the home of another.
Mrs. or Mistress - Was not always used to denote a married woman, but was a title of social position. A young woman coming from a higher class family would also be called "Mrs." even if unmarried. It was a frequent title used by the aristocracy.
Now Wife - Is not meant to convey that there had been a previous wife. But limits any bequest to the current wife only and not to subsequent future wives if any.(The exception is when the document refers to children by a first wife and children by a "present" or "Now" wife. In my research for this article I have found others who disagree and say that Now Wife always denotes that there was a previous wife.)
Natural Son - Does not denote an illegitimate son but indicates a relationship by blood as distinguished from a relationship by marriage or adoption. (In my research for this article I found others who disagreed and believed Natural Son always meant illegitimacy.)
Infant - Didn't necessarily mean a baby. It often meant a person under legal age, "Infant of Tender Years" would refer to a minor under the age of 14. Guardians were appointed for them by the Court. However if the wording for the court record reads that an "orphan came to court and chose as his guardian" you would know that the child was over 14 but under 21 if a male, and over 14 but under 18 if a female and unmarried. When a female married regardless of her age her legal rights passed automatically to her husband.
Goody - This is not a first name but a shortened title for Goodwife. A Goodwife is the spouse of a Goodman which is a title for a respected and solid member of the community who ranked above a Freeman but below a Gentleman on the social scale.

Misinterpreting these terms can certainly cause confusion with the branches of your family tree. Whenever possible verify the information that you get from older records. By evaluating how many arcane terms and spellings there are in a document you can determine how cautious you need to be with that particular record.