When writing your family history, it is important to understand how to properly use foreign words. These will often crop up when writing about your immigrant ancestor who came from a non-English-speaking background.
Foreign words that are not commonly understood or familiar should be set off in italics. For example:
The official motto of the province of Quebec is Je Me Souviens.
Foreign words familiar to English speakers, such as uno or mis en scène are not italicized. If you use both familiar and unfamiliar terms in the same context, you should either italicize both or keep both in Roman type for consistency. Proper nouns, such as person names or place names, are not italicized.
When using foreign words or phrases, a translation that follows should be set off in parentheses or quotation marks. For example:
Church records show that my great-great-grandfather was a cordonnier (shoemaker).
The importance of the proper use of diacritical marks in spelling foreign words cannot be overstated. Imagine what would happen if instead of describing your ancestor as a pêcheur (fisherman), you accidentally call him a pécheur (sinner)!
For more information about properly using foreign words, see The Chicago Manual of Style, 16th Edition.