知り合い

1. Origins, structure, and basic meaning

• Structure: 知り合い (しりあい) is an acquaintance, not necessarily a close friend. 知り合いに会う marks a person met; 知り合いがいない states absence.
• Basic usage: Someone unexpectedly meets a high-school acquaintance at a station; in a new town, no acquaintances are present.

2. Common pitfalls and similar expressions

• Acquaintance encountered and absence of local contacts
  • The person met takes に; the person whose existence is denied takes が. The relation can be looser than the friendship implied by 友人.