Possessive adjectives

Question

In the sentence "Apres, j'ai invite mes voisins a un aperitif pour faire leur connaissance", I would have thought "leur connaissance" should be plural (leurs connaissances) because she invited "mes voisins".

Maarten Kamp · Accepted Answer

Brett, 
This is a tricky area of grammar. 
The link below is to a response to a similar question and covers the fact that in 3rd person plural, when each person referred to has only 1 of the possession ( ‘ connaissance ‘ in this case ), both leur and the possession remain in the ‘ singular ‘  ( no added terminal  ‘s’ ) form. 
There is also a link to the topic on Laura Lawless site. 
https://french.kwiziq.com/questions/view/plural-singular-1

Anne Davies · Answer

Tricky indeed! i just did a writing exercise "My kids’ back-to-school day" where they packed "leurs cartables". I would’ve thought that although they might have more than one bag (for sports stuff, shoes, art etc) there would only be one satchel or "schoolbag" apiece. Clearly not.