"They invited their friend(s)"
How to distinguish four situations:
- They invited only one person, who is the common friend of all of them.
- They invited one friend for each of them.
- They invited one or more friend for each of them.
- They invited more than one friend for each of them.
“They invited only one person, who is the common friend of all of them” should at worst be “They invited one (person), the (common) friend of all.”
“They invited one friend for each of them” should be “They invited one friend each”.
“They invited one or more friend for each of them” should be “They invited one or more friends each” or “They each invited…”
“They invited more than one friend for each of them” should be “They invited more than one friend each” or “They each invited…”
– Robbie Goodwin Feb 23 '18 at 22:27