以後

1. Origins, structure, and basic meaning

• Structure: 以後, read いご, refers to time from a reference point onward.
• Basic usage: It is used for a time from which a door is locked or a period during which contact has ceased.
  • 午後六時以後は裏口が施錠されます。

2. Common pitfalls and similar expressions

• Including the reference time
  • When specifying a time, 午後六時以後 includes six in the evening and the time afterward. An English rendering should retain the sense of starting at that time, rather than merely being later.