以内

1. Origins, structure, and basic meaning

• Structure: 以内 is read as いない and is a range noun or suffix meaning within, or no more than, the preceding time, distance, or quantity.
• Basic usage: Use 一週間以内に提出する for a deadline and 歩いて十分以内です for travel time.

2. Common pitfalls and similar expressions

• The upper limit is included
  • Both one week and ten minutes remain inside the stated range, so the boundary value itself is allowed.
• Difference from 未満
  • 以内 includes the upper limit, while 未満 excludes the stated value; they are not interchangeable in exact constraints.