double · multiple

1. Origins, structure, and basic meaning

• Structure: 倍 expresses a multiple of a reference amount and is read ばい.
• Basic usage: 二倍 means twice the reference amount, and 倍増(ばいぞう) means doubling.

2. Common pitfalls and similar expressions

• Reference amount and total
  • 昨年の二倍 is the total relative to last year's amount. If there were 10 people last year, twice that number is 20.
• Asking for a multiple
  • 何倍(なんばい) asks how many times the reference amount. The surrounding context must establish what that reference is.