以下

1. Origins, structure, and basic meaning

• Structure: 以下 is read as いか and means at or below a stated limit, including that limit, or the content that follows.
• Basic usage: It can set a maximum age or point forward to a list of items presented next.

2. Common pitfalls and similar expressions

• Setting an upper limit
  • 十五歳以下 includes age fifteen itself as well as all younger ages. Example: 参加できるのは十五歳以下の子どもです。
• Referring to what follows
  • 以下の三点 points to the three items that are about to be presented. Example: 詳細は以下の三点にまとめました。