An alias is an alternative name a person was known by. Common reasons include a legal name change, adopting a new name on emigration, a child being registered under the mother’s maiden name before the parents married, or a surname alias of the kind parish registers write as "John Smith alias Jones".
Enter the alias name and type on the Naming tab of the Current Person Other Detail dialog (click the ‘…‘ button next to the name fields).
The type you choose decides how the alias reaches the page, and the two behaviours are quite different.
Some aliases are part of the name. "John Smith alias Jones" is not a sentence about a man, it is how the record writes his name, so Pedigree Forge writes it that way too — in the chapter title, in the narrative, in the child block of his parents’ chapter, and on charts. No separate sentence is produced, because the name has already said it.
Other aliases are an assertion about something that happened, or notably did not, so they appear as a clause: "James Jones assumed the surname Montague."
You do not have to remember which is which. Choose the type that describes the record and the right thing follows.
Where only part of the name changed, choose the type that names that part — a surname type where the surname changed, the given-names type where the given names varied. Only that part is then spoken of, so an unchanged forename is never pointlessly repeated.
Two types deserve a word.
Later surname is the non-committal one, and usually the right choice for a name change around a marriage or partnership. It records only that the person afterwards appears under another name — "Elizabeth Jones (later Smith-Jones)" — without claiming how or why it came about. It covers a husband taking his wife’s surname, a couple double-barrelling whether hyphenated or not, a new surname belonging to neither of them, and a partner’s surname taken without marriage. Put the circumstances in the alias text; the name itself stays honest about what the records actually show.
Kept own surname takes no name at all — the type is the whole statement. Use it for a woman who did not change her surname, which is worth saying precisely because a reader will otherwise assume she did. Like the option to show a person’s sex on a chart, it is there for the cases that are not obvious, so set it only where the point needs making.
A part-only alias gives the person two ways into the index. Someone recorded as Smith alias Jones is listed under both surnames, so a reader who only knows one of them can still find them.
If the alias does not support the type you have chosen — "assumed surname" against an alias with no surname in it, say — Pedigree Forge will not invent the missing part. It falls back to the general alias wording so that nothing you entered is lost from the book.
Note — Pedigree Forge supports one alias per person, so a person cannot carry both a register alias and one of the other types.